IO­390­A Series Maintenance and Overhaul Manual

August 2008
(Cover Revised June 2009)

© 2008 652 Oliver Street

Williamsport, PA 17701

Part No. LMO­IO­390­A Series

IO­390­A Series Maintenance and Overhaul Manual
Lycoming Part Number: LMO­IO­390­A Series

NOTE: The information contained in this manual applies to all certified IO­390­A series engines.

©2009 Lycoming. All rights reserved.

Lycoming and “Powered by Lycoming” are trademarks or registered trademarks of Lycoming.
Lycoming Engines, a division of AVCO Corporation, a wholly owned subsidiary of Textron Inc.

All brand and product names referenced in this publication are trademarks or registered
trademarks of their respective companies.

For additional information:

Mailing address:
Lycoming Engines
652 Oliver Street
Williamsport, PA 17701 U.S.A.

Phone:
Factory: 570­323­6181
Sales Department: 570­327­7278
Fax: 570­327­7101

Lycoming’s regular business hours are Monday through Friday from 8:00 A.M. through
5:00 P.M. Eastern Time (­5 GMT)

Visit us on the World Wide Web at:

http://www.lycoming.com

Revised June 2009

IO-390-A Series Maintenance and Overhaul Manual List of Effective Pages

List of Effective Pages

Chapter Section Page Date
05-00-00 Page 1 through Page 2 6/09
05-10-00 Page 1 through Page 2 6/09
05-20-00 Page 1 through Page 18 8/08
Page 19, Page 20 1/10
Page 21 through Page 24 8/08
05-50-00 Page 1 through Page 10 8/08
Page 11 6/09
Page 12 8/08
70-00-00 Page 1 through 16 8/08
72-00-00 Page 1, Page 2 6/09
Page 3, Page 4 8/08
Page 5 6/09
Page 6 through Page 40 8/08
Page 41 6/09
Page 42, Page 43 8/08
Page 44 1/10
Page 45 through Page 50 8/08
72-20-00 Page 1 through Page 2 8/08
72-30-00 Page 1, Page 2 8/08
Page 3 6/09
Page 4 through Page 20 8/08
72-50-00 Page 1 through Page 22 8/08
72-60-00 Page 1 6/09
Page 2 through Page 14 8/08
Page 15 10/10
Page 18, Page 19 6/09
Page 20 through Page 34 8/08
Page 35 6/09
Page 36 through Page 77 8/08
Page 78 6/09
Page 79 through Page 84 1/10
Page 85 through Page 116 8/08
Page 117 1/10
Page 118 10/10
Page 119, Page 120 8/08
Page 121 10/10
Page 122 through Page 131 8/08
Page 132, Page 133 6/09
Page 134 8/08
Page 135 6/09
Page 136 8/08
Page 137 6/09
Page 238 through Page 143 8/08

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List of Effective Pages IO-390-A Series Maintenance and Overhaul Manual

Chapter Section Page Date

72-60-00 (Cont.) Page 144 6/09
Page 145 8/08
73-00-00 Page 1 6/09
Page 2 8/08
73-10-00 Page 1 through Page 4 8/08
73-20-00 Page 1 through Page 4 8/08
74-00-00 Page 1 through Page 2 8/08
74-10-00 Page 1 through Page 8 8/08
74-20-00 Page 1 through Page 6 8/08
Appendix I I-1 through I-2 8/08
Appendix II II-1 through II-4 8/08
Appendix III III-1 through III-12 8/08
III-13 10/10
III-14, III-15 8/08
III-16 10/10
III-17 8/08
III-18 1/10
III-19, III-20 8/08
III-21, III-22 1/10
III-23 10/10
III-24 through III-27 8/08

iv Revised October 2010

IO-390-A Series Maintenance and Overhaul Manual Technical Publication Revision Log

Technical Publication Revision Log

Revision No. Publication Publication No. Publication Date

LMO-390-A-3 IO-390-A Series LMO-IO-390-A Series August 2008

Maintenance and
Overhaul Manual
The page(s) furnished herewith are intended to replace the corresponding page(s) of the publication
indicated above.
Previous revisions to this publication This revision consists of:

June 2009 October 2010

Cover Page, Title Page, Web Page List of Effective Pages, Page iii, iv
List of Effective Pages, Page iii, Page iv 72-60-00, Page 15
Introduction, Page 1 72-60-06, Page 118, 121
Section 05-00-00, Page 1, 2 Appendix III, Page III-13, III-16, III-23
Section 05-10-00, Page 1, 2
Section 05-50-06, Page 11
Section 72-00-01, Page 1, 2, 5
Section 72-00-06, Page 41
Section 72-30-02, Page 3
Section 72-60-01, Page 1
Section 72-60-02, Page 18
Section 72-60-03, Page 19
Section 72-60-05, Page 35
Section 72-60-06, Page 78, 117, 121, 132, 133
Section 72-60-07, Page 135
Section 72-60-08, Page 137
Section 72-60-09, Page 144
Section 73-00-01, Page 1

January 2010

List of Effective Pages, Page iii, Page iv

Technical Publication Revision Log, Page, v, iv
Section 05-20-06, Page 19, 20
Section 72-00-06, Page 44
Section 72-60-06, Page 79, 80, 81, 82, 83, 84, 117
Appendix III, Page III-13, III-16, III-18, III-21,
III-22, III-23, III-24, III-25, III-26, III-27

Revised October 2010 v

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vi Revised October 2010

IO-390-A1A6 Maintenance and Overhaul Manual Service Bulletin List

Lycoming IO-390-A1A6 Maintenance and Overhaul Manual

LMO-IO-390-A1A6

SERVICE BULLETIN LIST

Note: A date listed in the “SERVICE BULLETIN INCORPORATION DATE” column is the latest date
this report was revised to include changes to text/illustrations caused by a Service Bulletin or its
revision. When the words “No Effect” are listed, the Service Bulletin caused no changes within
this report.
SERVICE SERVICE
SERVICE BULLETIN BULLETIN
BULLETIN REVISION INCORPORATION
NUMBER NUMBER DATE SUBJECT

August 2008 vii

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This page intentionally left blank.

viii August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Record of Temporary Revisions

Lycoming IO-390-A1A6 Maintenance and Overhaul Manual

LMO-IO-390-A1A6

RECORD OF TEMPORARY REVISIONS

CHAP/SEC/ INCORPORATED
TR SUBJ ISSUE DATE DATE INTO MANUAL
NO. PAGE NO. DATE INSERTED BY REMOVED BY BY REV. NO.

August 2008 ix
Record of Temporary Revisions IO-390-A1A6 Maintenance and Overhaul Manual

This page intentionally left blank.

x August 2008
IO-390-A1A6 Maintenance and Overhaul Manual Record of Revisions

Lycoming IO-390-A1A6 Maintenance and Overhaul Manual

LMO-IO-390-A1A6

RECORD OF REVISIONS
ISSUE DATE ISSUE DATE
REV. NO. DATE INSERTED BY REV. NO. DATE INSERTED BY

August 2008 xi
Record of Revisions IO-390-A1A6 Maintenance and Overhaul Manual

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xii August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Compliance

Supplemental Service Information

Occasionally, Lycoming issues Service Bulletins, Service Instructions and
Service Letters which address maintenance and procedures not included in this
manual. Applicable information in these publications is at regular intervals
incorporated into Temporary or Permanent Revisions to this Manual.

Service Bulletins, Letters and Instructions are available from Lycoming

Distributors, or, by subscription, from the factory.

Manual Revision Information

This manual is current at the time of original issue.

Maintenance Manual revisions will be furnished to owners through Manual

Registration records, and are also available from the factory, or through your
Lycoming Distributor.

Temporary Revision
Important Maintenance information which requires prompt attention, such as
information included in Service Bulletins, will be provided by Temporary
Revisions to the manual. Temporary Revisions will be printed on colored paper
and will usually be replaced and superseded by a Permanent Revision.

Permanent Revision
When new or amended Maintenance information is available, it will be included
in Permanent Revisions. These Revisions also incorporate any Temporary
Revisions issued since the original issue or previous Permanent Revision.

All Revisions will be accompanied by a Technical Publications Revision Log

listing the type of Revision, the level of the Revision, the date of issue and
affected pages.

August 2008 xiii

Compliance IO-390-A1A6 Maintenance and Overhaul Manual

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xiv August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Table of Contents

Title Page
List of Effective Pages
Technical Publication Revision Log
Service Bulletin List
Record of Temporary Revisions
Record of Revisions
Supplemental Service Publications
Manual Revision Information
Table of Contents
List of Figures
List of Tables
Abbreviations and Acronyms
Introduction
Organization and Scope of This Manual
05-00-00 Airworthiness Limitations Section
05-10-00 Operating Limits
05-20-00 Inspection Program
05-20-01 10-Hour Inspection
05-20-01a Spectrographic Oil Analysis
05-20-01b Inspection Completion
05-20-02 25-Hour Inspection
05-20-02a Inspection Completion
05-20-03 50-Hour Inspection
05-20-03a General
05-20-03b Ignition System
05-20-03c Starter
05-20-03d Fuel and Induction System
05-20-03e Lubrication System
05-20-03f Exhaust System
05-20-03g Cooling System
05-20-03h Cylinders

August 2008 xv
Table of Contents IO-390-A1A6 Maintenance and Overhaul Manual

05-20-03i Wiring Inspection

05-20-03j Inspection Completion
05-20-04 100-Hour Inspection
05-20-04a General
05-20-04b Electrical System
05-20-04c Ignition System
05-20-04d Fuel Injector Nozzles and Lines
05-20-04e Engine Accessories
05-20-04f Cylinders
05-20-04g Engine Mounts
05-20-04h Inspection Completion
05-20-05 400-Hour Inspection
05-20-05a General
05-20-05b Cylinders
05-20-05c Inspection Completion
05-20-06 500-Hour Inspection
05-20-06a General
05-20-06b Magnetos
05-20-06c Inspection Completion
05-20-07 Mid-Life Inspection
05-20-07a Exhaust Valve and Guide Condition Inspection
05-20-07b Inspection Completion
05-20-08 2000-Hour Overhaul (TBO)
05-50-00 Unscheduled Maintenance
05-50-01 Aircraft Struck by Lightning
05-50-02 Propeller Strike, Sudden Engine Stoppage or Loss of a Propeller Blade Tip
05-50-03 Engine Operated with Unspecified Fuel
05-50-04 Engine Submersion
05-50-05 Fire
05-50-06 Overspeed

xvi August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Table of Contents

70-00-00 Standard Practices for Maintenance

70-00-01 Tools Recommended for Maintenance
70-00-02 Lockwire Practices
70-00-02a Lockwire Specifications
70-00-02b Basic Lockwiring Rules
70-00-02c Detailed Instructions for Lockwiring
70-00-03 Differential Pressure Compression Check
70-00-03a General
70-00-04 Cleaning
70-00-04a General
70-00-04b Precautions
70-00-05 Environmental Compliance
72-00-00 Reciprocating Engine Maintenance
72-00-01 General Description
72-00-01a Description of the Lycoming IO-390-A1A6 Engine
72-00-01b Engine Specifications
72-00-02 Operating Information
72-00-02a Pre-Start Checklist
72 00-02b Starting
72-00-02b1 Cold Engine
72-00-02b2 Hot Engine
72-00-02b3 Cold Weather Starting
72-00-02b4 Clearing a Flooded Engine
72-00-02b5 Ground Running and Warm-Up
72-00-02c Operations Checklist
72-00-02d Stopping and Shut-Down
72-00-02e Operation Ground Check after Maintenance
72-00-03 Troubleshooting
72-00-03a General
72-00-04 Engine Removal
72-00-04a Disconnecting the Engine
72-00-04b Removing External Accessories

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Table of Contents IO-390-A1A6 Maintenance and Overhaul Manual

72-00-04c Lifting
72-00-05 Long-Term Preservation
72-00-05a Active Engines
72-00-05b Inactive Engines
72-00-05c Fuel Injector Preservation
72-00-05d Factory Engine Preservation
72-00-06 Engine Installation
72-00-06a Uncrating
72-00-06b Uninhibiting
72-00-06b1 Engine
72-00-06c Fuel Injector
72-00-06d Installing the Engine
72-00-06e Connecting External Accessories
72-00-06f Pre-Oiling Engines Prior to Start
72-00-07 Engine Ordering and Return
72-00-07a Engine Ordering
72-00-07b Return of Runout Engines
72-00-07c Return of Engines for Special Adjustment Consideration
72-00-07d Parts Return ⎯ International
72-00-07e Parts Return ⎯ Domestic
72-20-00 Power Section Maintenance
72-20-01 General Information
72-20-02 Crankcase
72-20-03 Crankshaft and Counterweights
72-20-04 Camshaft
72-20-05 Bearings
72-30-00 Cylinder Section Maintenance
72-30-01 General Information
72-30-02 Cylinders
72-30-02a Compression Checks
72-30-02a1 Differential Compression Test Equipment Specifications

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IO-390-A1A6 Maintenance and Overhaul Manual Table of Contents

72-30-02a2 Recommendations for Performing the Differential Compression Check

72-30-02b Cylinder Removal
72-30-02c Cylinder Inspection
72-30-02d Cylinder Replacement
72-30-02e Exhaust Valve and Guide Condition Inspection
72-30-03 Rings
72-30-04 Pistons
72-30-05 Push Rods
72-30-06 Valves and Valve Springs
72-30-07 Roller Tappets
72-50-00 Lubrication System Maintenance
72-50-01 General Information
72-50-01a Lubricant Recommendations
72-50-01b Lubricant Additives
72-50-01c Lubricant Capacities
72-50-01d Recommended Oil/Filter Change Intervals and Procedures
72-50-02 Sump
72-50-02a Suction Screen
72-50-03 Oil Pump
72-50-04 Oil Pressure Relief Valve
72-50-04a Scheduled Maintenance
72-50-04b Pressure Adjustment
72-50-05 Oil Seals and Gaskets
72-50-06 Oil Cooler
72-50-07 Oil Cooler Bypass Valve
72-50-08 Oil Filter
72-50-08a Oil Filter/Screen Content Inspection
72-50-08b Spectrographic Oil Analysis
72-50-09 Oil Temperature Sensing System
72-60-00 Overhaul Section
72-60-01 Introduction

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Table of Contents IO-390-A1A6 Maintenance and Overhaul Manual

72-60-01a Disassembly Check List Procedure

72-60-02 Standard Practice for Overhaul
72-60-02a Tools Required for Overhaul
72-60-02b Cleaning
72-60-02c Inspection
72-60-02c1 General
72-60-02c2 Bearing Surfaces
72-60-02c3 Gears
72-60-02c4 Corrosion on Stressed Areas
72-60-02c5 Screwed Fittings
72-60-02c6 Magnetic Inspection
72-60-02d Repair and Replacement
72-60-02d1 Damaged Parts
72-60-02d2 Painted Parts
72-60-02d3 Aluminum and Steel Parts
72-60-02d4 Magnesium Parts
72-60-02d5 Shroud Tubes
72-60-02d6 Replacement of Studs
72-60-02d7 Corrosion Prevention
72-60-02e General Reassembly Procedures
72-60-02e1 Corrosion Prevention
72-60-02e2 Prelubrication of Parts Prior to Assembly
72-60-02e3 Oilite Bushings
72-60-02e4 Table of Limits
72-60-02e5 Oil Seals and Gaskets
72-60-02e6 Mandatory Replacement of Parts
72-60-02e7 Fuel Supply System
72-60-03 Overhaul of the Ignition System
72-60-03a General
72-60-03b Removal
72-60-03b1 Ignition Harness

xx August 2008
IO-390-A1A6 Maintenance and Overhaul Manual Table of Contents

72-60-03b2 Magnetos
72-60-03c Replacement
72-60-03d Reassembly
72-60-03d1 Magnetos
72-60-03d2 Installing the Magneto Drive Gear
72-60-03d3 Aligning the Magneto Rotor Shaft to Fire Cylinder #1
72-60-03e Adjustments
72-60-03e1 Timing Magneto to Engine
72-60-03e2 Ignition Harness
72-60-04 Overhaul of the Accessory Housing
72-60-04a Disassembly
72-60-04a1 Fuel Pump
72-60-04a2 Accessory Drive Assembly
72-60-04a3 Oil Filter
72-60-04a4 Removing the Accessory Housing from the Engine
72-60-04a5 Oil Pump
72-60-04a6 Oil Cooler Bypass Valve
72-60-04b Cleaning
72-60-04b1 Accessory Housing Parts
72-60-04c Inspection
72-60-04d Repair and Replacement
72-60-04e Reassembly
72-60-04e1 Oil Pump
72-60-04e2 Accessory Housing Installation
72-60-04e3 Vacuum Pump Drive Installation
72-60-04e4 Fuel Pump
72-60-04e5 Oil Filter and Filter Base
72-60-04e6 Oil Cooler Bypass Valve
72-60-05 Overhaul of the Cylinders, Pistons, and Valve Train
72-60-05a General Information
72-60-05b Cylinder Assembly Removal

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Table of Contents IO-390-A1A6 Maintenance and Overhaul Manual

72-60-05c Disassembly
72-60-05d Cleaning
72-60-05d1 Hydraulic Roller Tappets
72-60-05e Inspection
72-60-05e1 Cylinder Head (Visual Inspection)
72-60-05e2 Cylinder Head (Dimensional Inspection)
72-60-05e3 Cylinder Barrel (Visual Inspection)
72-60-05e4 Cylinder Barrel (Dimensional Inspection)
72-60-05e5 Piston Cleaning
72-60-05e6 Piston (Visual Inspection)
72-60-05e7 Piston (Dimensional Inspection)
72-60-05e8 Piston Pins and Piston Pin Plugs (Dimensional Inspection)
72-60-05e9 Valve Rockers
72-60-05e10 Valve Rocker Bushings
72-60-05e11 Push Rods
72-60-05e12 Valves
72-60-05e13 Detection of Magnetized Hydraulic Plunger Assemblies
72-60-05e14 Valve Springs
72-60-05f Modifications
72-60-05g Repair and Replacement – Cylinder Assembly
72-60-05g1 Spark Plug Thread Insert
72-60-05g2 Valve Seats
72-60-05g3 Valve Guides
72-60-05g4 Valve Rocker Thrust Washers
72-60-05g5 Valve Rocker Shaft Bushings
72-60-05g6 Cylinder Barrels
72-60-05g7 Valve Repair
72-60-05g8 Exhaust Flanges
72-60-05h Reassembly
72-60-05h1 Assembly of Pistons and Rings
72-60-05h2 Assembly of Cylinders

xxii August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Table of Contents

72-60-05h3 Installation of Pistons (After Crankcase and Crankshaft Assembly)

72-60-05h4 Installation of Cylinders
72-60-05h5 Installation of Cylinder Head Fin Stabilizers
72-60-05h6 Installation of Intercylinder Baffles
72-60-06 Overhaul of the Crankcase, Crankshaft, and Reciprocating Parts
72-60-06a Preparation
72-60-06b Crankcase Disassembly
72-60-06b1 Starter Ring Gear Support
72-60-06b2 Crankshaft Gear
72-60-06b3 Propeller Governor Drive Removal
72-60-06b4 Crankcase
72-60-06b5 Crankshaft
72-60-06b6 Counterweights
72-60-06c Cleaning
72-60-06c1 Piston Cooling Oil Nozzles
72-60-06d Inspection
72-60-06d1 Bearings (Precision Type)
72-60-06d2 Crankcase (Visual Inspection)
72-60-06d3 Crankcase (Dimensional Inspection)
72-60-06d4 Crankshaft (Visual Inspection)
72-60-06d5 Crankshaft (Dimensional Inspection)
72-60-06d6 Camshaft (Visual Inspection)
72-60-06d7 Camshaft (Dimensional Inspection)
72-60-06d8 Connecting Rods (Dimensional Inspection)
72-60-06d9 Connecting Rods (Parallelism Check)
72-60-06d10 Connecting Rods (Squareness Check)
72-60-06d11 Crankshaft Counterweight Bushings
72-60-06d12 Piston Cooling Oil Nozzles
72-60-06e Repair and Replacement
72-60-06e1 Crankshaft (Idler Shaft Recesses)
72-60-06e2 Crankshaft (Bearing Surfaces)

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Table of Contents IO-390-A1A6 Maintenance and Overhaul Manual

72-60-06e3 Crankshaft (Reconditioning Worn Oil Seal Surfaces)

72-60-06e4 Crankshaft (Straightening Flange)
72-60-06e5 Crankshaft (Counterweight Bushing Replacement)
72-60-06e6 Counterweights (Inspection, Replacement, and Balancing)
72-60-06e7 Connecting Rod Bushings
72-60-06e8 Crankshaft and Gear Assembly
72-60-06e9 Starter Ring Gear
72-60-06f Reassembly
72-60-06f1 Plug
72-60-06f2 Propeller Flange Bushings
72-60-06f3 Crankshaft Gear
72-60-06f4 Counterweight Assembly
72-60-06f5 Connecting Rods
72-60-06f6 Camshaft
72-60-06f7 Crankcase
72-60-06f8 Propeller Governor Drive
72-60-06f9 Crankcase Assembly
72-60-06f10 Crankshaft Oil Seal Installation
72-60-06f11 Drive Belt and Ring Gear Support
72-60-06f12 Crankshaft Idler Gears
72-60-07 Overhaul of the Induction System
72-60-07a General Information
72-60-07b Disassembly
72-60-07b1 Intake Pipes
72-60-07b2 Fuel Injector
72-60-07b3 Induction Housing
72-60-07b4 Oil Sump Removal
72-60-07c Cleaning and Inspection
72-60-07d Reassembly
72-60-08 Overhaul of the Fuel Supply and Fuel Injection System
72-60-08a General Information
72-60-08b Disassembly

xxiv August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Table of Contents

72-60-08b1 Fuel Supply Lines

72-60-08b2 Fuel Injector
72-60-08c Cleaning
72-60-08c1 Fuel Injector Nozzle Assemblies
72-60-08d Inspection
72-60-08d1 Nozzle Assembly
72-60-08e Repair and Replacement
72-60-08e1 Fuel Injector
72-60-08e2 Fuel Pump
72-60-08f Reassembly
72-60-08f1 Fuel Injector
72-60-08f2 Flow Divider
72-60-08f3 Air Bleed Nozzles
72-60-08f4 Fuel Lines Inspection
72-60-08f5 Fuel Line Installation
72-60-09 Testing and Run-In Following Overhaul
72-60-09a General
72-60-09a1 Test Stand
72-60-09a2 Test Instruments and Equipment
72-60-09a3 Test Stand Oil Supply Pressure
72-60-09b Test Limits
72-60-09c Run-In Procedure
72-60-09d Oil Consumption Run
72-60-09e Idle Speed and Mixture Adjustment
72-60-09e1 Idle Air Bleed Adjustment
73-00-00 Engine Fuel and Control Maintenance
73-00-01 General Description
73-00-01a Fuel Recommendations
73-00-01b Fuel Capacity
73-10-00 Fuel Distribution
73-10-01 Fuel Distribution
73-10-01a Fuel Line Routing and Clamping
73-10-01b Fuel Pump Replacement

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Table of Contents IO-390-A1A6 Maintenance and Overhaul Manual

73-10-01c Fuel Nozzles

73-10-01d Fuel Filter
73-10-01e Air Intake Ducts and Filters
73-20-00 Fuel Control
73-20-01 Fuel Control
73-20-01a Fuel Injector
73-20-01a1 Cleaning and Replacement of Inlet Screen and Strainer O-rings
73-20-01a2 Idle Speed and Mixture Adjustments
73-20-01a3 Fuel Injector Removal
73-20-01a4 Cleaning
73-20-01a5 Fuel Injector Nozzles
73-20-01a6 Inspection
73-20-01a7 Nozzle Assembly
73-20-01a8 Fuel Flow Check
74-00-00 Ignition System Maintenance
74-00-01 General Description
74-10-00 Electrical Power Supply System Maintenance
74-10-01 General Description
74-10-02 Retard Magnetos
74-10-03 Alternator
74-10-04 Starter
74-20-00 Electrical Power Distribution System Maintenance
74-20-01 General Description
74-20-02 Ignition Harness
74-20-03 Spark Plugs
74-20-03a Removal and Installation
74-20-03b Maintenance Procedures
Appendix I: Parts Catalog
Appendix II: Engine Performance Data
Appendix III: Table of Limits

xxvi August 2008

IO-390-A1A6 Maintenance and Overhaul Manual List of Figures

List of Figures
Figure Number Figure Title Page
1 Sample Registration Card ........................................................................................ 2
2 Top View of Engine................................................................................................. 3
72-00-01-1 Oil System Schematic Diagram ....................................................................3, 72-00
72-00-04-1 Lifting Lugs and Engine Mounts ................................................................31, 72-00
72-30-02-1 Typical Differential Compression-Measuring Device ..................................3, 72-30
72-30-02-2 Gage Adapter Assembled on Exhaust Stem................................................10, 72-30
72-30-02-3 Compressor Plate Installed on Cylinder......................................................10, 72-30
72-30-02-4 View Showing Screwdriver in Position to Move Exhaust Valve Stem ......11, 72-30
72-30-02-5 Feeler Gage in Position Between Set Screw and Adapter Post ..................12, 72-30
72-30-02-6 Details for Modifying Tool ST-310 for Use with a Dial Indicator
(Angle Valve Cylinders) ...........................................................................13, 72-30
72-30-02-7 Dial Indicator in Position to Check Valve Guide Clearance.......................14, 72-30
72-30-02-8 Pushing Valve Stem and Adapter Post Toward Dial Indicator to
Establish Valve Guide Condition..............................................................15, 72-30
72-30-02-9 View Through Exhaust Port Showing Mechanical Fingers Holding
Valve Stem................................................................................................16, 72-30
72-60-03-1 Slick Magneto Drive Assembly ..................................................................20, 72-60
72-60-03-2 Marked Teeth on Crankshaft Idler Gear .....................................................21, 72-60
72-60-03-3 Ignition Wiring Diagram.............................................................................25, 72-60
72-60-04-1 Fuel Pump Assembly ..................................................................................27, 72-60
72-60-04-2 Accessory Drive Adapters ..........................................................................28, 72-60
72-60-04-3 Oil Pump Assembly and Accessory Housing Attaching Parts....................30, 72-60
72-60-05-1 Angle Valve Cylinder Assembly ................................................................35, 72-60
72-60-05-2 Two Methods of Supporting Connecting Rods ..........................................37, 72-60
72-60-05-3 Removing Push Rod Socket........................................................................38, 72-60
75-60-05-4 Removing Hydraulic Tappet Plunger Assembly ........................................38, 72-60
72-60-05-5 Hydraulic Roller Tappets............................................................................40, 72-60

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List of Figures IO-390-A1A6 Maintenance and Overhaul Manual

Figure Number Figure Title Page

72-60-05-6 Maximum Fin Removal ..............................................................................42, 72-60
72-60-05-7 Section Through Cylinder Assembly Showing Locations for Diameter
Checking and Removal of Wear Step .......................................................44, 72-60
72-60-05-8 Method of Checking Piston Ring Side Clearance.......................................46, 72-60
72-60-05-9 Area to Inspect on Valve Stems..................................................................46, 72-60
72-60-05-10 Valve Showing Locations for Checking Run-Out and Section for
Measuring Edge Thickness .......................................................................47, 72-60
72-60-05-11 Section Through Edge of Valve..................................................................47, 72-60
72-60-05-12 Method of Checking Valve Edge Thickness with a Dial Indicator ............48, 72-60
72-60-05-13 Appearance of Spalling Marks on Face of Hydraulic Tappet Bodies.........49, 72-60
72-60-05-14 Rockwell Marks ..........................................................................................50, 72-60
72-60-05-15 Appearance of Interior Shoulder in New and Worn Tappet Bodies ...........50, 72-60
72-60-05-16 Chipped Shoulder .......................................................................................51, 72-60
72-60-05-17 Checking Plunger Assembly.......................................................................52, 72-60
72-60-05-18 Checking the Hydraulic Plunger Assembly for Leaks................................52, 72-60
72-60-05-19 Valve Seat Removal Tool ...........................................................................55, 72-60
72-60-05-20 Valve Seat Dimensions for Reconditioning................................................60, 72-60
72-60-05-21 Rejection of Valve Seat ..............................................................................61, 72-60
72-60-05-22 Piston Assembly .........................................................................................64, 72-60
72-60-05-23 Cylinder Assembly .....................................................................................66, 72-60
72-60-05-24 Cylinder Reassembly ..................................................................................69, 72-60
72-60-05-25 Sequence of Tightening Cylinder Base Nuts ..............................................71, 72-60
72-60-06-1 Crankcase and Related Parts .......................................................................75, 72-60
72-60-06-2 Crankshaft and Associated Parts.................................................................77, 72-60
72-60-06-3 IO-390-A1A6 Crankcase ............................................................................78, 72-60
72-60-06-4 Illustrative Example of Camshaft Wired to Crankcase Half.......................78, 72-60
72-60-06-5 Propeller Governor Drive ...........................................................................79, 72-60
72-60-06-6 Crankcase Assembly ...................................................................................80, 72-60

xxviii August 2008

IO-390-A1A6 Maintenance and Overhaul Manual List of Figures

Figure Number Figure Title Page

72-60-06-7 Crankshaft and Counterweight Assembly...................................................81, 72-60
72-60-06-8 Location of Idler Shaft Recesses in Crankcase ...........................................85, 72-60
72-60-06-9 Camshaft with Integral Gears .....................................................................86, 72-60
72-60-06-10 Checking Parallelism of Connecting Rods .................................................87, 72-60
72-60-06-11 Checking Squareness of Connecting Rods .................................................88, 72-60
72-60-06-12 Piston Cooling Nozzle Test ........................................................................89, 72-60
72-60-06-13 Machining of Cranckase for Idler Shaft Bushings......................................90, 72-60
72-60-06-14 Detail of Idler Shaft Bushing for Crankcase...............................................91, 72-60
72-60-06-15 Idler Shaft Installation in Crankcase...........................................................91, 72-60
72-60-06-16 Reconditioning Crankshaft Oil Seal Surfaces.............................................94, 72-60
72-60-06-17 Limits for Straightening Bent Flanges ........................................................96, 72-60
72-60-06-18 Removal of the Crankshaft Counterweight Bushing ..................................98, 72-60
72-60-06-19 Crankshaft Counterweight Lug Bushing Reamer (ST-280)........................99, 72-60
72-60-06-20 Installing Counterweight Bushing Using Fixture ST-93 and
Driver ST-92 ...........................................................................................102, 72-60
72-60-06-21 Identification of Dimensions “A” and “B” ...............................................103, 72-60
72-60-06-22 Depth Gage Adjusted with Set-Master Preparatory to Checking Line
Position of Counterweight Bushings ......................................................105, 72-60
72-60-06-23 Checking Centerline Position of Counterweight Using Gage
Fixture ST-94..........................................................................................106, 72-60
72-60-06-24 Checking Parallelism and Squareness of Counterweight Bushings
with Gage Fixture ST-91 (Vertical Position)..........................................106, 72-60
72-60-06-25 Checking Parallelism and Squareness of Counterweight Bushings
with Gage Fixture ST-91 (Horizontal Position)......................................107, 72-60
72-60-06-26 Counterweight Mounted on ST-96 Arbor for Balancing ..........................108, 72-60
72-60-06-27 Counterweight Balanced by Weight ST-95 Placed One Inch
from Center ..............................................................................................108, 72-60
72-60-06-28 Location of Areas on Counterweight for Grinding...................................109, 72-60
72-60-06-29 Crankshaft and Gear Assembly.................................................................110, 72-60
72-60-06-30 Section Through End of Crankshaft Showing Driven Height of
STD-1065 Dowel and Dowel Details .....................................................112, 72-60

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List of Figures IO-390-A1A6 Maintenance and Overhaul Manual

Figure Number Figure Title Page

72-60-06-31 Section Through End of Crankshaft Showing Driven Height of
STD-2078 Dowel and Dowel Details .....................................................112, 72-60
72-60-06-32 Details for Repairing Pilot Diameter of Crankshaft..................................113, 72-60
72-60-06-33 Minimum Dimension of Crankshaft .........................................................113, 72-60
72-60-06-34 Section Through Ring Gear Support.........................................................115, 72-60
72-60-06-35 Crankshaft Plug Location .........................................................................116, 72-60
72-60-06-36 Type 2 Propeller Flange Bushing Location ..............................................117, 72-60
72-60-06-37 Rear End View of Crankshaft Showing Associated Parts ........................118, 72-60
72-60-06-38 Assembly of Washer and Circlip in Counterweight .................................119, 72-60
72-60-06-39 Location of Gap When Installing Retaining Rings...................................120, 72-60
72-60-06-40 Connecting Rod Bolt Nut .........................................................................122, 72-60
72-60-06-41 Illustrative Example of Camshaft Wired to Crankcase Half.....................125, 72-60
72-60-06-42 Checking the Crankshaft End Clearance ..................................................126, 72-60
72-60-06-43 Sealing Area for P.O.B. Sealant and “00” Silk Thread.............................128, 72-60
72-60-06-44 Sealing Area for RTV-102 and Loctite-5 15 ............................................128, 72-60
72-60-06-45 Crankcase Tightening Sequence ...............................................................129, 72-60
72-60-06-46 Right Side of Crankcase Showing Bolts Installed on Thru-Studs ............130, 72-60
72-60-06-47 Right Side of Crankcase Showing Plate Assembled Over Bolts ..............130, 72-60
72-60-06-48 Right Side of Crankcase Showing Pressure Plate Utilized to Pull
Halves of Crankcase Together ................................................................130, 72-60
72-60-06-49 Crankshaft Propeller Flange Showing the Installation of the Stretch
Seal..........................................................................................................131, 71-60
72-60-06-50 Idler Gear Diagram ...................................................................................133, 72-60
72-60-07-1 IO-390-A1A6 Induction System...............................................................135, 72-60
72-60-08-1 Minimum Fuel Line Bending Dimensions................................................140, 72-60
72-60-08-2 IO-390-A1A6 Fuel Supply System...........................................................141, 72-60
72-60-09-1 RSA-5AD1 Fuel Injector ..........................................................................149, 72-60
73-10-01-1 Fuel Pump Replacement ...............................................................................1, 73-10

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IO-390-A1A6 Maintenance and Overhaul Manual List of Figures

Table of Limits Figures

Figure Number Figure Title Page
Figure 1 Crankcase and Crankshaft Dimension ................................................................III-5
Figure 2 Connecting Rod Dimension................................................................................III-5
Figure 3 Crankshaft and Camshaft Dimension .................................................................III-6
Figure 4 Tappet Dimension...............................................................................................III-6
Figure 5 Counterweight Dimension ..................................................................................III-6
Figure 6 Connecting Rod and Piston Dimension ............................................................III-11
Figure 7 Valve and Valve Rocker Dimension.................................................................III-11
Figure 8 Oil Pump Dimension.........................................................................................III-14
Figure 9 Crankshaft Idler Gear Dimension .....................................................................III-15
Figure 10 Fuel Pump Dimension.......................................................................................III-15
Figure 11 Propeller Governor Idler Gear Dimension........................................................III-15
Figure 12 Hydraulic Pump Dimension..............................................................................III-16
Figure 13 Vacuum Pump and Tachometer Drive Dimension ...........................................III-16
Figure 14 Magneto Bearing Gear and Crankcase Torque .................................................III-16
Figure 15 Allowable Gear Backlash Dimension ...............................................................III-18
Figure 16 Piston Cooling Nozzle ......................................................................................III-21
Figure 17 Adjustable Oil Relief Valve Torque .................................................................III-21
Figure 18 Fuel Injector Nozzle Torque .............................................................................III-21
Figure 19 Fuel Injection Line Union Nut Torque .............................................................III-21
Figure 20 Connecting Rod Bolt and Cylinder Hold-Down Nut Torque ...........................III-22
Figure 21 Spark Plug and Exhaust Port Stud Torque........................................................III-23
Figure 22 Magneto Nut and Plate Screws Torque.............................................................III-23
Figure 23 Hose Clamp Torque ..........................................................................................III-24
Figure 24 Alternator Pulley Nut and Auxiliary Terminal Nut Torque..............................III-24
Figure 25 Oil Filter Torque ...............................................................................................III-25
Figure 26 Outer and Inner Valve Spring ...........................................................................III-26

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xxxii August 2008

IO-390-A1A6 Maintenance and Overhaul Manual List of Tables

List of Tables

Table Number Table Title Page

05-10-00A Operating Limits ...........................................................................................1, 05-10
70-00-02A Lockwire Specifications................................................................................3, 70-00
70-00-02B Lockwiring Methods.....................................................................................6, 70-00
72-00-01A IO-390-A1A6 Engine Specifications ............................................................5, 72-00
72-00-06A Accessory Drives ........................................................................................42, 72-00
75-50-01A Lubricating Oil Recommendations ...............................................................1, 72-50
72-60-02A Tools Required for Overhaul ........................................................................3, 72-60
72-60-05A Intake Valve Edge Thickness......................................................................48, 72-60
72-60-05B Valve Seat Replacement Tools ...................................................................57, 72-60
72-60-05C Valve Guide Replacement Tools ................................................................59, 72-60
75-60-05-D Washer Part Numbers and Sizes .................................................................61, 72-60
72-60-05-E Push Rod Part Numbers and Lengths .........................................................73, 72-60
72-60-06A Crankshaft Undersize Codes.......................................................................92, 72-60
72-60-06B Counterweight Bushing Size Chart.............................................................99, 72-60
72-60-06C Tap Chart ..................................................................................................111, 72-60
72-60-06D Dowels and Dowel Holes..........................................................................114, 72-60
72-60-06E Propeller Flange Bushing Location ..........................................................117, 72-60
72-60-08A Replacement Fuel Lines and Clamps........................................................147, 72-60
72-60-09A IO-390-A1A6 Engine Run-In Test Limits ................................................150, 72-60
72-60-09B IO-390-A1A6 Ground Run-In Chart ........................................................152, 72-60
72-60-09C IO-390-A1A6 Text Flight Chart ...............................................................153, 72-60
72-60-09D Recommended Run-In Schedule...............................................................154, 72-60
72-60-09E Engine Run-In after Overhaul...................................................................158, 72-60
73-00-01A Specified Fuel Grade Comparison Chart ......................................................2, 73-00
74-00-01A Ignition System Components........................................................................1, 74-00

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xxxiv August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Abbreviations and Acronyms

Abbreviations and Acronyms

A
AD Ashless Dispersant (oil)
AD Airworthiness Directive
AFM Aircraft Flight Manual
Alt. Altitude
Amb. Ambient
AMP Ampere
API American Petroleum Institute
ASME American Society of Mechanical Engineers

B
BHP Brake Horsepower (per hour)
BMEP Brake Mean Effective Pressure
BDC Bottom Dead Center
BSFC Brake Specific Fuel Consumption
BTU British Thermal Unit

C
C Celsius
Cad. Cadmium
cc Cubic Centimeters
CCW Counterclockwise
CFM Cubic Feet per Minute
CFS Cubic Feet per Second
CHT Cylinder Head Temperature
CL. Centerline
CR Compression Ratio
Cu.-Ft. Cubic Foot (Feet)
Cu.-In. Cubic Inch(es)
Cyl. Cylinder

D
Deg. Degree (also °)
Dia. Diameter

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Abbreviations and Acronyms IO-390-A1A6 Maintenance and Overhaul Manual

D (cont.)
Diff. Differential
Dwg. Drawing

E
EGT Exhaust Gas Temperature
EPA Environmental Protection Agency
EPT External Pipe Thread
Ex. Example

F
F Fahrenheit
FAA Federal Aviation Administration
FAR Federal Aviation (and Space) Regulation
Fed. Federal
Ft.-lb. Foot Pound (torque)

G
GPH Gallons per Hour
GPM Gallons per Minute

H
Hex. Hexagon
Hg Mercury
HP Horsepower

I
IAS Indicated Airspeed
ICA Instructions for Continued Airworthiness
ID Inside Diameter
IHP Indicated Horsepower
in.-lb. Inch Pound (torque)
in. inch, inches
Inj. Injector, injected
IPT Internal Pipe Thread
IR Inside Radius

xxxvi August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Abbreviations and Acronyms

L
lb. Pound
LL Low Lead (fuel)

M
Mag. Magneto
MAP Manifold Air Pressure
Max. Maximum
MEK Methyl-ethyl-ketone
MEP Mean Effective Pressure
Mg Magnesium
Min. Minimum
ml/USgal Milliliter per U.S. gallon
Mo Molybdenum
MP Manifold Pressure

N
NAS National Aircraft Standard
Ni Nickel
NPT National Pipe Taper (thread)

O
OAT Outside Air Temperature
Oct. Octane
OD Outside Diameter
OR Outside Radius
OS Oversize
Oz. Ounce

P
P/N Part Number
ppm Particles per Million
psi Pounds per square inch
psia Pounds per square inch absolute
psig Pounds per square inch gage

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Abbreviations and Acronyms IO-390-A1A6 Maintenance and Overhaul Manual

Q
Qty. Quantity

R
R Radius
Ref. Refer, reference
RPM Revolutions per Minute

S
SAE Society of Automotive Engineers (oil viscosity)
SB Service Bulletin
Sect. Section
SI Service Instruction
SL Service Letter
Sol. Solenoid
Spec. Specification
Sq. Ft. Square Foot (Feet)
Sq. In. Square Inch (es)
STC Supplemental Type Certificate
Std. Standard
Sys. System

T
T/N Tool Number
Tach. Tachometer
TBO Time Between Overhauls
TC Type Certificate, Type Certification
TDC Top Dead Center
Tech. Technical, technician, technology
TEL Tetraethyl Lead
Temp. Temperature
TIR Total Indicator Reading

U
UL Unleaded (gasoline)

xxxviii August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Abbreviations and Acronyms

V
V Volt, Voltage
Vol. Volume

W
Wt. Weight

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Abbreviations and Acronyms IO-390-A1A6 Maintenance and Overhaul Manual

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xl August 2008
IO-390-A Series Maintenance and Overhaul Manual Introduction

Introduction
Organization and Scope of This Manual
This manual contains the necessary information and procedures for maintaining
and overhauling the Lycoming IO-390-A Series engine and is in compliance with
FAR 33.4. Individuals responsible for engine maintenance or overhaul should
thoroughly read this information before beginning any procedure. It is essential
to follow these instructions to ensure safe operation and to contribute to the long
life, economy, and satisfactory functioning of this engine.
The IO-390-A Series PC-409-1 Parts Catalog, referenced in Appendix A must be
used in conjunction with this Manual.
In accordance with the requirements of 33.5 of Federal Aviation Regulations
Installation and Operating Instructions are provided in the FAA Approved IO-
390-A Series Operation and Installation Manual (Lycoming P/N 60297-34).
Every effort has been made in preparing this manual to ensure its accuracy.
However, any comments, suggestions, or corrections to this manual are welcome
and should be directed, in writing, to:
Technical Publications Coordinator
Lycoming Engines
652 Oliver Street
Williamsport, PA 17701
Additionally, Lycoming has a Customer Service Hot Line to provide information
and assistance to owners, operators, and maintenance personnel servicing
Lycoming engines. The number for the Customer Service and Technical Support
Hot Line is (570) 323-6181 between the hours of 8:00 A.M. and 5:00 P.M. EST
(-5 GMT) Monday through Friday.
For a period of 3 years, new and revised pages for this manual will be furnished
to individuals who fill out and return the enclosed manual registration card. At 3
years a renewal option will be mailed. A sample registration card is shown in
Figure 1.
Conventions
This manual uses the following Notes, Cautions and Warnings.

Note: Read for added information and reminders.

Caution Equipment damage may result if instructions are not

followed.

Warning Personal injury could result if instructions are not

followed.

Revised June 2009 1

Introduction IO-390-A1A6 Maintenance and Overhaul Manual

Figure 1. Sample Registration Card

Revisions are also available from the factory or from your Lycoming Distributor.

This manual is based on the Air Transport Association (ATA) format. It provides
airworthiness limits in Section 05-00-00 and operating limits in Section 05-10-
00. Sections 05-20-00 through 05-20-05 describe scheduled maintenance, and
Section 05-50-00 outlines unscheduled maintenance. A description of the engine,
its specifications, operating information, and troubleshooting data are given in
Sections 72-00-01 through 72-00-03. Sections 72-00-04 through 72-00-07
include detailed instructions for removing the engine for overhaul or for long-
term storage, as well as instructions for reinstallation and testing. Procedures for
routine engine servicing and maintenance are arranged by major engine system.
Overhaul procedures are included in Sections 72-60-00 through 72-60-08.
Appendix I details engine parts. Engine performance charts are included in
Appendix II, and a Table of Limits including standard torque requirements is
provided in Appendix III.

Note: The owner of the manual is responsible for notifying the factory of a
change of address.

In this manual, all references to locations of various components will be

designated as if viewing the engine from the rear (or anti-propeller) end. The
front of the engine is considered to be the propeller end and the oil sump is
considered to be on the bottom of the engine. Cylinders are numbered from front
to rear with the odd-numbered cylinders on the right-hand side. The firing order
for this engine is 1-3-2-4.

2 August 2008
IO-390-A1A6 Maintenance and Overhaul Manual Introduction

Figure 2. Top View of Engine

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Introduction IO-390-A1A6 Maintenance and Overhaul Manual

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4 August 2008
IO-390-A1A6 Maintenance and Overhaul Manual Reference

DISASSEMBLY CHECK LIST PROCEDURE

• Disconnect leads and wiring

• Remove accessories

• Remove intake pipes

• Remove drainback tubes

• Remove all connecting control cables

• Remove fuel injector

• Remove fuel lines and clamps

• Remove induction housing

• Remove oil sump

• Remove oil sump baffle

• Remove intercylinder baffles

• Remove spark plugs

• Remove rocker box covers

• Remove rocker shaft cover plates

• Remove rocker shafts, rockers, push rods, shroud tubes and valve rotator
caps. Keep parts separate for reassembling in the correct location.

• Remove cylinders and pistons

• Remove connecting rods one at a time. Insure connecting rods are supported.

• Split crankcase

• Remove crankshaft and camshaft and bearings

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6 August 2008
IO-390-A Series Maintenance and Overhaul Manual Section 05-00-00

05-00-00 AIRWORTHINESS LIMITATIONS SECTION

05-00-01 GENERAL
This Airworthiness Limitations section sets forth each mandatory replacement
time, inspection interval, and related procedure required for type certification.
The Airworthiness Limitations section is FAA Approved and specifies
maintenance required under §§ 43.16 and 91.403 of the Federal Aviation
Regulations unless an alternative program has been FAA Approved.

A bold red parallel line pattern in the outside margin of a page denotes an
Airworthiness Limitation Section.

05-00-02 MANDATORY REPLACEMENT

At every 500 hours of operation, replace both magnetos with serviceable parts.
Refer to Section 05-20-06b.

05-00-03 MANDATORY INSPECTION – EXHAUST VALVE AND GUIDE

At every 1000 hours of operation, inspect the Exhaust Valve and Guide
condition. Refer to Section 05-20-07a.

05-00-04 MANDATORY INSPECTION – FUEL INJECTOR LINES

At every 100 hours of operation, at each overhaul, and after any maintenance has
been performed on the engine where the fuel injector lines have been
disconnected, moved, or loosened, reinspect the fuel injector lines in accordance
with Section 72-60-08f4.

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Page 2, Section 05-00 Revised June 2009

IO-390-A Series Maintenance and Overhaul Manual Section 05-10-00

05-10-00 Operating Limits

The operating limits for the IO-390-A Series engine is listed in Table 05-10-00A.

Table 05-10-00A. Operating Limits

Oil Pressure

Starting, Warm-up,
Taxi, and Take-off
(Maximum) 115 psi

Normal 55 to 95 psi

Minimum Idling 25 psi

Oil Temperature Maximum Optimum for Engine Life

235°F (113°C) 180°F (82°C)

Oil Consumption Maximum Qt./Hr.

Normal 1.0

Performance (75% 0.75

Rated)

Economy (60% Rated) 0.60

Exhaust Back Pressure The exhaust back pressure must not exceed 2 in.
of mercury at any cylinder to minimize the
installed horsepower losses.

Fuel Pressure at Engine Fuel Pump Inlet Operating Conditions Fuel Pressure

Psi above ambient air pressure at the engine fuel Maximum 35 psi
pump
Minimum -2 psi

Note: Fuel pressure (lb./sq.in. above injector deck pressure) at the inlet to the fuel injector will be 14 to
45 psi for normal operation.

Revised June 2009 Page 1, Section 05-10

Section 05-10-00 IO-390-A Series Maintenance and Overhaul Manual

Specified Fuel Grade (ASTM-D910-75) Color Max. TEL m1/US gal.

100LL Blue 2.0

100 Blue 2.0

Notes:
1. In some countries, Grade 100LL is colored green and designated as 100L.
2. If the specified fuel is not available, a higher grade may be used. The use of higher grades
should be limited and requires more frequent (25 hours) inspection of combustion chambers,
valves, and valve ports for lead deposits. Any time lead oufling is experienced, spark plugs
should be rotated and cleaned.

Caution
Never use automotive fuel in aircraft engines, regardless of octane or advertised features
because of the corrosive effect of high chlorine content and because vapor lock can result
from high vapor pressure. Any fuel used in this engine must conform to ASTM-D910 or
MIL-G-5572F specifications.
Refer to Table 73-00-01 for Fuel Grade Comparison Chart.

Cylinder Temperature The maximum permissible cylinder head

temperature as measured with a bayonet-type
AN5541 thermocouple is 450°F (240.56°C) above
75% power and 435°F (224°C) at 75% power and
below.

Temperature Correction All temperatures must be corrected in accordance

with FAA factors.

Page 2, Section 05-10 Revised June 2009

IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-00

05-20-00 INSPECTION PROGRAM

Strict adherence to this inspection program and prompt correction of any
discrepancies are essential to obtaining maximum performance, safety, durability
and continued airworthiness of the engine and its components.

The inspections contained in this section does not constitute a complete aircraft
inspection but is meant as a guideline for maintaining only the engine. Comply
with the requirements of the aircraft manufacturer, accessory manufacturer, and
any manufacturers of components or systems that have Supplemental Type
Certificates (STC).

The inspection program is contained in Sections 05-20-01 through 05-20-08 of

this Manual.

Note: Inspection intervals may not be exceeded by more than 10 hours, to

allow time en route to the inspection facility. See FAR 91.409 for further
requirements.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-01

05-20-01 10-HOUR INSPECTION

In new, rebuilt, or newly overhauled engines, the following procedures must be
performed after the first 10 hours of operation.

05-20-01a Spectrographic Oil Analysis

Refer to Section 72-50-08b

05-20-01b Inspection Completion

1. Correct all discrepancies identified by this inspection before returning the

engine to service.

2. Comply with all applicable Airworthiness Directives.

3. Perform an operational ground check in accordance with section 72-00-02

and the airframe manufacturer’s instruction manual.

4. Record and correct any discrepancies

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-02

05-20-02 25-HOUR INSPECTION

In a new, rebuilt or newly overhauled engine, the procedures which are specified
in the 50-Hour Inspection (05-20-03a) must be performed after the first 25 hours
of operation.

1. Drain and renew lubrication oil with a straight mineral type, aviation grade
lubrication oil (refer to Table 72-50-01a).

2. Inspect oil filter and screen (refer to section 05-20-01a).

3. Comply with all applicable Airworthiness Directives.

05-20-02a Inspection Completion

1. Correct all discrepancies identified by this inspection before returning the

engine to service.

2. Comply with all applicable Airworthiness Directives.

3. Perform an operational ground check in accordance with section 72-00-02

and the airframe manufacturer’s instruction manual.

4. Record and correct any discrepancies.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-03

05-20-03 50-HOUR INSPECTION

05-20-03a General
Perform the following maintenance checks after the first 50 hours of operation
and every 50 hours thereafter:

1. Confirm that all ignition and electrical switches are in the “off” position.

2. Follow the aircraft manufacturer’s manual to ensure the ignition switch is

operating correctly.

3. Following the aircraft manufacturer’s instructions, drain a sample of each

fuel sump and inspect the samples to ensure they contain only clean aviation
grade 100 or 100LL fuel. Whenever water or sediment is found, continue
draining samples from sumps until all traces of water or sediment have been
removed.

4. Prior to any pre-inspection cleaning of the engine, check for evidence of

fluid leaks, residues, or discoloration and investigate and correct the source.

5. Clean engine in accordance with Section 70-00-04.

6. Repair or replace any missing or damaged components in accordance with

the airframe manufacturer’s manual.

7. Visually inspect the cowling and nacelles for evidence of fuel or oil leaks.

8. Isolate the source of any leaks and correct before returning the engine to
service.

9. Visually inspect the engine for evidence of fuel or oil leaks.

10. Isolate the source of any leaks and correct.

11. Inspect fuel and oil lines for leakage, security, signs of chafing, kinks, or
other physical damage.

12. Correct any discrepancies noted.

13. In accordance with the airframe manufacturer’s instructions, visually inspect

the induction air filter for cleanliness, security, and evidence of damage.

14. Replace any filters with holes or tears in accordance with the aircraft
manufacturer’s instructions.

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Section 05-20-03 IO-390-A1A6 Maintenance and Overhaul Manual

Note: Clean the induction air filter daily when operating in dusty conditions or
when otherwise indicated. Refer to the airframe manufacturer’s manual
for servicing instructions.

15. Ensure that all shields and cowling are in place and secure.

16. Check all engine controls for general condition, full travel, and freedom of
operation in accordance with the airframe manufacturer’s instructions.

05-20-03b Ignition System

1. Confirm that the P-leads are securely attached to the magneto condenser
studs. Torque P-lead nut to 13-15 in. lbs. as required.

2. Rotate the spark plugs by moving the bottom plugs to the upper position
whenever operational ground checks indicate evidence of spark plug fouling.
See Table below.

SPARK PLUG ROTATION

Interchange
#1 Top with #4 Bottom
#2 Top with #3 Bottom
#3 Top with #2 Bottom
#4 Top with #1 Bottom

3. Remove spark plug connector nuts and examine spark plug cable leads and
ceramics for corrosion and deposits. Corrosion and deposits are evidence of
leaking spark plugs or of improper cleaning of the spark plug walls or
connector ends.

4. Recondition or replace affected spark plugs as necessary, being certain plugs

are of the correct heat range.

5. Clean the cable ends, spark plug walls, and ceramics with a clean lint-free
cloth moistened with methyl-ethyl-ketone (MEK), acetone, or wood alcohol.

6. Replace any broken, cracked, deformed, or corroded parts.

7. Dry all parts using compressed air.

8. Visually inspect the ignition harness for evidence of chafing or deterioration.

Replace the harness assembly if any leads are worn, damaged, or broken.
Refer to section 74-20-01a.

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9. Ensure the security of ignition harness mounting clamps.

10. Verify that the spark plug and magneto terminal connections are tight.

11. Correct any discrepancies noted.

05-20-03c Starter
Kelly Aerospace

1. Clean corrosion from electrical terminals.

2. Clean the starter drive and shaft with oleum or mineral spirits, and lubricate
with silicon spray every 50 hours.

Sky-Tec

1. There are no 50-hour inspection requirements for Sky-Tec starters.

05-20-03d Fuel and Induction System

1. Visually inspect all fuel lines and fuel fittings for evidence of damage or
leaks.

2. Replace any fuel lines that are crimped or kinked. Cracks can develop at the
site of bends or kinks.

3. Ensure the security of the clamps.

4. Remove and clean the fuel inlet strainers. Always remove from the inlet side.
Refer to section 73-20-01.

5. Check the mixture control and throttle linkage for full travel, freedom of
movement, and security of the clamps. Follow the aircraft manufacturer’s
procedures to lubricate linkage.

6. Tighten clamps as necessary.

7. Inspect air intake ducts for leaks, security, and filter damage. Evidence of
dust or other solid material in the ducts is indicative of inadequate filter care
or of a damaged filter. Service in accordance with aircraft manufacturer’s
maintenance procedures as necessary.

05-20-03e Lubrication System

1. Check for visual evidence of oil, fuel or hydraulic fluid leaks. Locate the
sources of the leaks and repair.

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Section 05-20-03 IO-390-A1A6 Maintenance and Overhaul Manual

2. Refer to the airframe manufacturer’s instructions for additional inspections.

3. Drain the lubricating oil.

4. Remove and inspect the oil suction screen and filter element for signs of
metal contamination. Refer to section 72-50-08a.

5. Clean the oil suction screen in the oil sump and reinstall and safety.

6. Install new oil filter, torque and safety.

7. Renew the lubricating oil with approved aviation grade oil. Refer to section
72-50-01.

8. Dispose of used oil, oil filter, and elements in compliance with all applicable
federal, state, and local environmental requirements.

9. Run engine and recheck for leaks. Refer to section 72-00-02e, Operation
Ground Check After Maintenance.

Caution
Failure to inspect the oil suction screen and the oil filter element for
metal particles, or ignoring what is found, can lead to catastrophic engine
failure.

Note: Lycoming Product Support Division provides a metal analysis service for
new, rebuilt, or factory-overhauled Lycoming engines under warranty.
Contact Product Support for additional information and instructions.

Note: Switching from straight mineral oil to an ashless dispersant-type oil is

acceptable after the first 50 hours of engine operation, provided that the
rings have seated and oil consumption has stabilized. The maximum
allowable oil consumption is 1 quart per hour, as calculated by the
formula: .0032 x BHP = qt/hr. Refer to Table 05-10-00A.

05-20-03f Exhaust System

1. Remove all baffles, heat shields and other airframe or engine components
that may interfere with the inspection of the exhaust system.

2. Visually inspect the exhaust flange to exhaust port connections for a

powdery white to light brown or black residue indicating exhaust leakage.

3. Follow the aircraft manufacturer’s instructions to correct any leaks.

4. Replace blown gaskets.

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5. Retorque loosened gasket flange assemblies. Refer to Table of Limits for

torque values.

Caution
Exhaust gas leakage between the exhaust flange and exhaust port pad
will quickly erode the aluminum cylinder head. When this occurs,
resurfacing the cylinder port may be required to reestablish a seal. Refer
to Overhaul Section 72-60-05g.

6. Examine exhaust manifolds for visible damage such as bulging, cracks,

dents, residue and overall general condition. Correct deficiencies in
accordance with airframe or exhaust manufacturer’s procedures.

05-20-03g Cooling System

1. Check cowling and baffles for physical damage and secure anchorage.

2. Repair or replace any damaged or missing parts of the cooling system in

accordance with the airframe manufacturer’s maintenance manual.

05-20-03h Cylinders

1. Visually inspect rocker box covers for evidence of oil leaks.

2. Replace any leaking gaskets and tighten the screws to 50 in. lbs.

3. Visually inspect cylinders for evidence of excessive heat as indicated by

burned paint on the cylinder. This condition is evidence of internal damage
to the cylinder. Determine the cause and correct. Inspect and repair cylinder
and/or engine as necessary. Refer to sections 72-60-05 and 72-60-06.

Note: Heavy discoloration and evidence of seepage at cylinder head and barrel
attachment area are usually due to the emission of thread lubricant used
during assembly of the barrel at the factory, or by slight gas leakage that
stops after the cylinder has been in service for a while. This condition is
neither harmful nor detrimental to engine performance and operation.

05-20-03i Wiring Inspection

Inspect all electrical wiring for proper routing, security, clamping, wear, and
chafing per the airframe manufacturer’s instructions. Do not allow the electrical
wiring to contact inappropriate surfaces like fuel lines.

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Section 05-20-03 IO-390-A1A6 Maintenance and Overhaul Manual

05-20-03j Inspection Completion

1. Correct all discrepancies identified by this inspection before returning the

engine to service.

2. Comply with all applicable Airworthiness Directives.

3. Perform an operational ground check in accordance with section 72-00-02

and the airframe manufacturer’s instruction manual.

4. Record and correct any discrepancies.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-04

05-20-04 100-HOUR INSPECTION

05-20-04a General
In addition to the 50-hour inspection, perform the following additional
maintenance checks after every 100 hours of operation. Before beginning, it is
important to clean the engine exterior so that any defects or flaws will be evident.

05-20-04b Electrical System

1. Inspect all wiring connections to the engine and accessories for physical
damage and security.

2. Follow the aircraft manufacturer’s instructions for replacement of any

damaged cables or clamps.

3. Inspect the terminals for security and cleanliness.

4. Clean and tighten as necessary. Refer to Appendix III for appropriate torque
values.

05-20-04c Ignition System

1. Verify that the magneto-to-engine timing is 20° before top dead center.

2. Adjust the timing as necessary. Refer to section 72-60-03.

3. Inspect wiring connections and conditions.

4. Clean the magneto vents to insure that there is no obstruction.

5. Inspect P-lead attachment which is labeled on the magneto. Correct torque

for P-lead attachment is 13-15 in.-lbs. Follow the airframe manufacturer’s
recommendations to insure the ignition switch and P-lead are operating
properly.

Warning
If the P-lead is disconnected, the magneto will be ON and will fire the
spark plug if the propeller is rotated. To avoid possibly fatal injury,
confirm that the P-lead is securely attached to the condenser stud.

6. Insure that the switch wire on the retard (left) breaker connects the retard
contact points to the ignition vibrator.

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Section 05-20-04 IO-390-A1A6 Maintenance and Overhaul Manual

7. Remove, clean, inspect, gap, test and rotate the spark plugs. Replace if
necessary. Refer to Section 05-20-03b.

05-20-04d Fuel Injector Nozzles and Lines

1. Check fuel injector nozzle line attachments for looseness. Tighten the fittings
in accordance with Table of Limits.

2. Visually inspect each fuel line between the fuel injector manifold and the
nozzles for any evidence of physical damage and for stains caused by fuel
leakage. Replace as required.

Caution
Do not attempt to repair a damaged fuel line. Replace any line that is
cracked, dented, or kinked; cracks can develop at the site of sharp bends
or kinks.

3. Inspect solder joints at the end of lines for cracks. Replace cracked lines.

4. Examine the routing of fuel lines and location of the clamps that secure the
fuel lines to the engine. Refer to Figure 72-60-08-1 and section 72-60-08f4.

5. Examine the lines to ensure that the clamps securely support the line.

6. Visually inspect the lines, hoses, and clamps for evidence of chafing, leaking,
improper conditions, and looseness.

7. Examine the flexible hoses. Replace any hoses that have become hard.

8. Inspect hoses, gaskets, and seals for deterioration or leakage. Replace any
hoses, gaskets, or seals that contain evidence of these conditions.

Caution
Each person approving a reciprocating engine-powered aircraft for return
to service after an annual or 100-hour inspection must, before that
approval, run the aircraft engine or engines to determine satisfactory
performance in accordance with the manufacturer’s recommendations of
power output (static and idle rpm), magnetos, fuel and oil pressure, and
cylinder and oil temperature.

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05-20-04e Engine Accessories

1. Examine the engine controls for defects, improper travel, and improper
safetying.

2. Check for security and apparent defects in engine-mounted accessories such

as pumps and temperature- and pressure-sensing units.

3. Confirm that the alternator support bracket and mounting are tight.

4. Refer to Appendix III for torque requirements and tighten as required.

05-20-04f Cylinders

1. Examine the cylinders for cracked or broken fins.

2. Check the cylinder compression in accordance with section 72-30-02a.

3. Repair or replace the cylinders as necessary. Refer to section 72-30-02.

05-20-04g Engine Mounts

1. Check for cracks, looseness of mounting, and looseness of the engine.

2. Examine the rubber engine mounts and mounting hardware for signs of
deterioration or damage. Service or replace in accordance with airframe
manufacturer’s instructions.

3. Confirm the proper torque values for engine-mounting, bracket-attaching

nuts or bolts after the first 100 hours of operation following engine
installation or replacement. Refer to Table of Limits for torque values.

05-20-04h Inspection Completion

1. Correct all discrepancies identified by this inspection before returning the

engine to service.

2. Comply with all applicable Airworthiness Directives.

3. Perform an operational ground check in accordance with section 72-00-02

and the airframe manufacturer’s instruction manual.

4. Record and correct any discrepancies.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-05

05-20-05 400-HOUR INSPECTION

05-20-05a General
In addition to the 50-hour inspection, and the 100-hour inspection, perform the
following inspection items.

05-20-05b Cylinders

1. Remove rocker box covers.

2. Look for evidence of abnormal wear or broken parts in the area of the valve
tips, valve keeper, springs, and spring seats. If any of these indications are
found, remove the cylinder and all of its components (including the piston
and connecting rod assembly) and inspect for further damage. Refer to
sections 72-60-05 and 72-30-00.

3. Refer to the Table of Limits in Appendix III and replace any parts that do not
conform to the limits shown.

05-20-05c Inspection Completion

1. Correct all discrepancies identified by this inspection before returning the

engine to service.

2. Comply with all applicable Airworthiness Directives.

3. Perform an operational ground check in accordance with section 72-00-02

and the airframe manufacturer’s instruction manual.

4. Record and correct any discrepancies.

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IO-390-A Series Maintenance and Overhaul Manual Section 05-20-06

05-20-06 500-HOUR INSPECTION

05-20-06a General
In addition to the 50-hour inspection, the 100-hour inspection, and the 400 hour
inspection, perform the following inspection items.

05-20-06b Magnetos
Replace the magnetos with serviceable units in accordance with Airworthiness
Limitations Section. Refer to Overhaul Section 72-60-03.

05-20-06c Inspection Completion

1. Correct all discrepancies identified by this inspection before returning the
engine to service.

2. Comply with all applicable Airworthiness Directives.

3. Perform an operational ground check in accordance with section 72-00-02e

and the airframe manufacturer’s instruction manual.

4. Record and correct any discrepancies.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-07

05-20-07 MID-LIFE INSPECTION

In addition to the 50-hour, the 100-hour, the 400-hour and the 500-hour
inspections, at halfway to the recommended TBO or 1000 hours, whichever
occurs first.

05-20-07a Exhaust Valve and Guide Condition Inspection

Inspect Exhaust Valves and Guides in accordance with the Airworthiness
Limitations Section. Refer to Maintenance Section 72-30-02e.

05-20-07b Inspection Completion

1. Correct all discrepancies identified by this inspection before returning the

engine to service.

2. Comply with all applicable Airworthiness Directives.

3. Perform an operational ground check in accordance with section 72-00-02

and the airframe manufacturer’s instruction manual.

4. Record and correct any discrepancies.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-20-08

05-20-08 2000-HOUR OVERHAUL (TBO)

At 2000 hours of operating time, or 12 years from the date the engine is put in
service, whichever occurs first, the engine is recommended to be overhauled in
accordance with section 72-60-00 or returned to the factory for rebuild.

All engine accessories are recommended to be replaced with serviceable units at

the time the engine is overhauled.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-50-01

05-50-00 UNSCHEDULED MAINTENANCE

05-50-01 AIRCRAFT STRUCK BY LIGHTNING
Damage to an aircraft that has been struck by lightning is usually apparent and
often confined to a specific area of the structure. In such instances where the
engine and its accessories, controls, fuel, or exhaust systems are involved, it is
necessary to evaluate and repair the damage before the aircraft is flown again.

Although the path of the lightning may appear to have been around the external
housings of the engine components, it is impossible to assess the internal damage
that might have occurred by heat during the lightning discharge. Heat generated
by the arcing effect of the electrical discharge can cause irreparable damage to
the hardened surfaces of ball bearings, crankshaft bearing surfaces, camshaft
lobes, gear teeth, and other parts that are surface hardened.

A complete overhaul of the engine is required. Disassemble and inspect the

engine in accordance with the overhaul section of this manual (section 72-60-00).
Parts that show evidence of discoloration, cracks, or other indications of damage
by lightning must not be reused.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-50-02

05-50-02 PROPELLER STRIKE, SUDDEN ENGINE STOPPAGE OR

LOSS OF A PROPELLER BLADE TIP
Sudden engine stoppage, propeller strike, or loss of a propeller blade or tip may
result in unseen internal engine damage and subsequent engine failure.

A propeller strike is defined as follows:

1. Any incident, whether or not the engine is operating, that requires repair to
the propeller other than minor dressing of the blades.

2. Any incident during engine operation in which the propeller impacts a solid
object which causes a drop in RPM and also requires structural repair of the
propeller (incidents requiring only paint touch up are not included). This is
not restricted to propeller strikes against the ground, and although the
propeller may continue to rotate, damage to the engine may result, possibly
progressing to engine failure.

3. A sudden RPM drop while impacting water, tall grass, or similar non-solid
medium, where propeller structural damage is not normally incurred.

The above definitions encompass any propeller strike occurring at taxi speeds,
including touch-and-go operations involving propeller tip ground contact. In
addition, they also include situations where an aircraft is stationary and the
landing gear collapses causing one or more blades to be substantially bent, or
where a hangar door (or other object) strikes the propeller blade. These cases
should be handled as sudden engine stoppage because of potentially severe side
loading on the crankshaft flange, front bearing and seal.

Circumstances which surround accidents are many and varied; therefore, the
circumstances of the accident can not, in our opinion, be used to predict the
extent of the damage to the engine or assure its future reliability.

Lycoming must take the position that in the case of a sudden engine stoppage,
propeller/rotor strike or loss of propeller/rotor blade or tip, the safest procedure is
to remove and disassemble the engine and completely inspect the case and the
reciprocating and rotating parts including crankshaft gear and dowel parts.
Accessories must be inspected per the component’s instructions for continued
airworthiness from the component’s manufacturer. Any decision to operate an
engine which was involved in a sudden stoppage, propeller/rotor strike or loss of
propeller/rotor blade or tip without such an inspection must be the responsibility
of the agency returning the aircraft to service.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-50-03

05-50-03 ENGINE OPERATED WITH UNSPECIFIED FUEL

Refer to Section 73-00-01a for Specified Fuels.

The primary damage to the engine caused by the use of unspecified fuels occurs
in the combustion chambers. Damage is typically characterized by tuliped intake
valves and burned pistons. This damage results from the increased temperatures
and pressures from detonation. In severe cases, detonation damage may not be
limited to the intake valves and pistons. The main bearings and other valve train
components may show excessive wear due to lack of lubrication. The detuning of
the engine counterweights and resultant overstressing of the crankshaft may also
occur.

A complete overhaul of the engine is required. Disassemble and inspect the

engine in accordance with the overhaul section (Section 72-60-00) of this
manual.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-50-04

05-50-04 ENGINE SUBMERSION

Damage to the engine due to submersion is caused by the introduction of
moisture and foreign materials into the entire system.

A complete overhaul of the engine is required. Disassemble and inspect the

engine in accordance with the overhaul section (Section 72-60-00) of this
manual.

Note: The composition of the substance that the engine has been exposed to
can affect the type and extent of damage.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 05-50-05

05-50-05 FIRE
Heat damage to an engine is difficult to assess; therefore any components
exposed to the heat of a fire must be replaced.

Disassemble and inspect the engine in accordance with the overhaul section
(Section 72-60-00) of this manual.

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IO-390-A Series Maintenance and Overhaul Manual Section 05-50-06

05-50-06 OVERSPEED
The IO-390-A Series is rated at 2700 RPM, above which it cannot be operated
safely. Operation above rated engine speed can accelerate the wear on stressed
parts and possibly result in their damage or failure.

Momentary overspeed is defined as an increase of no more than 10% above rated

speed for a period not exceeding 3 seconds.

Any instance of overspeed must be recorded in the engine log along with the
corrective action taken.

For the IO-390-A Series:

Rated engine speed - 2700 RPM

5% overspeed - 2835 RPM

10% overspeed - 2970 RPM

If overspeed is between 2700 and 2835 RPM for 3 seconds or less, comply with
item 1, below.

If overspeed is between 2835 and 2970 RPM for 3 seconds or less, comply with
items 1 and 2, below.

If overspeed exceeds 2700 RPM for more than 3 seconds or if speed exceeds
2970 RPM for any length of time, comply with item 3, below.

1. Determine the cause for the overspeed and correct it.

2. Drain the lubricating system.

a. Remove screens and filters and inspect for metal contamination (see 72-
50-08a).

b. Perform differential pressure check on all cylinders to determine the

sealing quality of the rings and valves (see 70-00-03a).

c. Using a 4x borescope with a 70° angle of view or similar equivalent

internal examining device, examine the walls of each cylinder for
scoring, which could be evidence of stuck or broken piston rings.
Determine the condition of the intake and exhaust valve faces and seat
faces. Evidence of wear, pounding, or grooving is reason to replace
valves and seats.

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Section 05-50-06 IO-390-A1A6 Maintenance and Overhaul Manual

d. Inspect the internal condition of valve keys, rockers, and exhaust valve
guides for damage; particularly check valve springs for coil strikes or
severe bottoming of the coils. If damage to the springs is evident, remove
them and check compression load in accordance with the Table of
Limits; replace springs that are not within limits.

e. Rotate the crankshaft by hand to determine if the valve lift is uniform or

equal for all cylinders; also note if valve rockers are free when the valves
are closed. Unequal lift indicates bent push rods; tight rockers when
valves are closed indicate a tuliped valve or damaged valve lifter. Repair
all suspected damage before returning the engine to service.

f. Refer to 72-30-02d to determine exhaust valve stem to valve guide

clearance condition.

3. Remove the engine from the aircraft; disassemble it and inspect the parts in
accordance with the Overhaul Section of this manual (section 72-60-00).
Replace damaged parts and parts that are not within the service limits shown
in the Table of Limits. Bushings must be replaced in both counterweight and
crankshaft.

4. Remove, inspect and replace if necessary the accessories per the

components’ instructions for continued airworthiness from the components’
manufacturer.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-01

70-00-00 STANDARD PRACTICES FOR MAINTENANCE

70-00-01 TOOLS RECOMMENDED FOR MAINTENANCE
In addition to a standard set of mechanic’s tools, the following tools are
recommended.

Tool No. Nomenclature and Description

64593 Expanding and Staking Tool, 18 mm Spark Plug Heli-coil Insert

64594 Inserting Tool, 18 mm Spark Plug Heli-coil Insert

64595 Removing Tool, 18 mm Spark Plug Heli-coil Insert

64697 Pointer, Ignition Timing

64942 Wrench (1/2 in. Allen) Cylinder Base Nut

64943 Wrench (3/8 in. Allen) Cylinder Base Nut

ST-71 Fixture

ST-310-9 Gage Adapter

ST-489 Wrench, Shroud Tube

ST-288 Socket, Spark Plug Wrench (7/8 in. Hex)

Champion Oil Filter Cutting Tool

CT-470 or
Airwolf
AFC-470

N/A Differential Compression Tester (See Figure 72-30-02-1)

N/A Borescope, 4x With a 70° Angle of View

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-02

70-00-02 LOCKWIRE PRACTICES

Lockwiring is a method of wiring together units in a manner that any tendency of
one to loosen is counteracted by the tightening of the wire.

70-00-02a Lockwire Specifications

Lockwire material for use up to 700°F must be a corrosion resistant steel such as
AMS 5685. Lockwire material for applications up to 1800°F must be a corrosion
and heat resistant steel such as AMS 5687. Refer to Table 70-00-02A, Lockwire
Specifications, for the specified diameters.

The majority of lockwiring applications on the engine will use 0.032 in. diameter
lockwire. Use wire with a minimum nominal size of 0.016 in. for parts with hole
diameters too small to accommodate 0.032 in. wire. Table 70-00-02A shows wire
sizes and tolerances.

Table 70-00-02A. Lockwire Specifications

Wire Diameter 700°F 1800°F

(In.) Tolerance AMS 5685 AMS 5687 Twists
(± In.) Ref. P/N Ref. P/N Per In.

0.016 0.001 ---- MS9226-01 11-14

0.020 0.001 ---- MS9226-02 9-12

0.025 0.001 AS100027 MS9226-03 9-12

0.032 0.002 AS100028 MS9226-04 7-10

0.040 0.002 AS100029 MS9226-05 7-10

0.051 0.002 AS100030 MS9226-06 5-8

0.063 0.002 AS100031 MS9226-07 5-8

0.091 0.002 ---- MS9226-08 4-7

70-00-02b Basic Lockwiring Rules

1. The “double-twist” method is the most common method of installing

lockwire. It consists of two strands of wire twisted together through an arc of
180°. Half of a complete turn defines “one twist.”

2. Use the single strand method of lockwiring, when specified, to secure closely
spaced, closed geometrical pattern parts (triangle, square, rectangle, circle,

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Section 70-00-02 IO-390-A1A6 Maintenance and Overhaul Manual

etc.) and electrical system parts. In such cases, limit the single strand wire to
the pattern or group of similar parts.

3. When joining widely spaced multiple groups by the double-twist method, the
maximum acceptable number to join in series is three.

4. When lockwiring closely spaced groups using the single strand method, the
maximum number of units that can be joined is determined by a 24-in. length
of wire.

5. Install lockwire in a manner that does not overstress it. Lockwire will break
under vibrations if twisted too tightly. Pull the wire taut while twisting to
produce a twist with the approximate number of twists per inch indicated in
Table 70-00-02A.

6. Exercise caution to prevent the wire from becoming nicked, kinked, or

otherwise mutilated. Nicked, kinked or otherwise mutilated wire is
unacceptable.

7. Install lockwire in a manner that will not cause additional tension other than
the tension imposed on the wire to prevent loosening.

8. Install lockwire in a manner that will not cause chafing or fatigue through
vibration.

9. Lockwire parts without holes to a convenient neighboring part. Lockwire in a

manner that does not interfere with the function of the parts following the
basic principles.

10. The maximum span of lockwire allowed between tension points is six in.
unless otherwise specified.

11. Use new lockwire for each application.

12. When a drawing specifies a seal, apply and crimp the seal to the lockwire
ends remaining after completing a series.

13. Lockwire hose and electrical coupling nuts in the same manner as for tube
coupling nuts.

14. Figures A through CC show typical examples of lockwiring. Figure K shows

an example of the single strand method, while the other figures show the
double-twist method. Adhere to the basic rules outlined in this section for all
lockwiring.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-02

70-00-02c Detailed Instructions for Lockwiring

1. Check the units to be lockwired to ensure that they have been correctly
torqued. Undertorquing or overtorquing to obtain proper alignment of the
holes is unacceptable. Back off the unit and try again or select another unit
when it is impossible to obtain proper alignment within the specified torque
limits.

2. The holes in adjacent units should be approximately the same in relationship

to each other, as shown in Figures A through D for right-hand threads. Install
the lockwire in a manner that the strand through the hole has a tendency to
pull to the right. Reverse for left-hand threads.

3. Insert the lockwire through the first unit and either bend the upper end over
the head of the unit or around it. If bent around it, loop the upper end under
the strand protruding from the hole and ensure the direction of the wrap and
twist will tend to keep the loop down.

4. Twist the strands taut until the twisted part is just short of the hole in the next
unit. The twisted portion should be within 1/8 in. from the hole in either unit.

5. When the free strand is to be bent around the head of the second unit, insert
the uppermost strand through the hole in this unit and follow the rules in
paragraph 2. If there are more than two units in the series, repeat the above
procedure.

6. Twist the wires to form a pigtail of three to five twists after wiring the last
unit. Cut off the excess wire, exercising extreme care to prevent the cut-off
wire ends from falling into the engine. Bend the pigtail toward the part in a
manner as that prevents it from becoming a snag. Short pigtails are desirable
when vibration is likely.

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Section 70-00-02 IO-390-A1A6 Maintenance and Overhaul Manual

Table 70-00-02B. Lockwiring Methods

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-02

Table 70-00-02B cont. Lockwiring Methods

August 2008 Page 7, Section 70-00

Section 70-00-02 IO-390-A1A6 Maintenance and Overhaul Manual

Table 70-00-02B cont. Lockwiring Methods

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-02

Table 70-00-02B cont. Lockwiring Methods

August 2008 Page 9, Section 70-00

Section 70-00-02 IO-390-A1A6 Maintenance and Overhaul Manual

Table 70-00-02B cont. Lockwiring Methods

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-03

70-00-03 DIFFERENTIAL PRESSURE COMPRESSION CHECK

70-00-03a General
The differential compression check measures pressure leakage through the
combustion chamber. Compression testing equipment enables the mechanic to
detect leaks due to improper valve seating, worn piston rings, or damaged pistons
and cylinders.

The differential compression tester operates on the principal that, for a given
airflow through a fixed orifice, a constant pressure drop across that orifice will
result.

Compression testing enables a mechanic to detect leaks due to improper valve

setting, worn piston rings, or damaged pistons and cylinders. The condition of the
working parts in the combustion chamber of a cylinder can be determined by
measuring the static leak rate of the cylinder in terms of pressure drop through an
orifice of specified size. The cylinder compression is determined by attaching a
differential compression-measuring device to one spark plug hole of the cylinder
while the piston is at TDC of the compression stroke.

Compression testing is recommended any time the engine exhibits a loss of

power, increased oil consumption, hard starting, or other evidence of abnormal
operation.

The differential compression tester operates on the principle that, for a given
airflow through a fixed orifice, a constant pressure drop across that orifice will
result. Refer to Figure 72-30-02-1.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-04

70-00-04 CLEANING

70-00-04a General

1. Prior to engine disassembly, ensure that the work area is clean.

2. Benches on which engine parts are placed must be clean and free from grit,
metal filings, etc., which may contaminate engine oil systems, fuel systems
or hardware.

3. Clean plastic bags should be available in which oil system and fuel system
parts may be stored until ready for reassembly.

4. Clean plastic caps or covers should be used to protect exposed tubes or

bearing areas.

5. At reassembly make sure that all parts are clean and new packings installed.

70-00-04b Precautions
Note: The choice of cleaning agents should be limited to approved
consumables complying with local, state and federal regulations. The
toxicity of cleansing agent will, however, depend on the type of
contamination encountered on part to be cleaned.

Caution
Take particular care in selecting cleaning method to make sure that
protective coatings are not removed from parent metal. Do not use alkalis
on aluminum, magnesium, aluminized and painted areas.

1. Wear rubber gloves, apron or coveralls and face shield or goggles, when
working with solvents.

2. Use the least toxic of available cleaning materials which will satisfactorily
accomplish work.

3. Do all cleaning operations in a well ventilated work area.

4. Make sure that adequate and usable fire fighting and safety equipment is
conveniently located and available to all personnel.

5. Do not smoke or expose a flame within 50 feet of cleaning area.

6. Make sure that all degreasing agents are thoroughly removed from all parts
after cleaning.

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Section 70-00-04 IO-390-A1A6 Maintenance and Overhaul Manual

7. Do no use steel brushes for any cleaning operation except when specifically
detailed within this manual. Use a stiff bristle fiber brush.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 70-00-05

70-00-05 ENVIRONMENTAL COMPLIANCE

Lycoming is concerned with preserving the environment.

Whenever solvents, paint, fuel, oil, chemicals, or other consumables are used in
operating, maintaining, or overhauling an engine or component, Lycoming
strongly urges engine owners and repair and overhaul personnel to observe and
comply with all federal, state, and local environmental regulations.

Please share our concern for, and commitment to, clean earth, clean water, and
especially clean air for succeeding generations of flyers.

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Page 16, Section 70-00 August 2008

IO-390-A Series Maintenance and Overhaul Manual Section 72-00-01

72-00-00 RECIPROCATING ENGINE MAINTENANCE SECTION

72-00-01 GENERAL DESCRIPTION

72-00-01a Description of the Lycoming IO-390-A Series Engine

The Lycoming IO-390-A Series engine is fuel-injected, direct-drive, four-
cylinder, horizontally opposed, and air-cooled with a down exhaust. These
engines are supplied with a starter. Mounting pad drives for two AN-type
accessories and a propeller governor are included.

FAA Type Certificate Number E00006NY has been issued for this engine.

The IO-390-A Series engine has a rated maximum continuous power of 210 hp at
2700 rpm at standard sea level conditions. These engines have a bore of 5.319
in., a stroke of 4.375 in., a piston displacement of 389 cubic inches, and a
compression ratio of 8.9:1.

The nitrided cylinders are air-cooled with the major parts (head and barrel)
screwed and shrunk together. The heads are made from an aluminum alloy
casting with a fully machined combustion chamber. Valve guides and valve seats
are shrunk into machined recesses in the head. Rocker shaft bearing supports are
cast integrally with the head along with the housings to form the rocker boxes for
both intake and exhaust valve rockers.

The Lycoming IO-390-A Series engine incorporates a color coding system

painted on the cylinder heads to designate the specific cylinder barrels and spark
plugs required. The IO-390-A Series engine has nitrided cylinders, indicated by
blue paint between the shroud tubes, and requires long-reach spark plugs,
indicated by yellow paint between the spark plug and the rocker box cover.

Cylinder barrels are machined from a chrome nickel molybdenum steel forging
with deep integral cooling fins. The interiors of the barrels are ground and honed
to a specified finish.

The valve-operating mechanism employs a conventional camshaft located above

and parallel to the crankshaft. The camshaft actuates tappets which operate the
valves through push rods and valve rockers.

Roller tappets are used to compensate for any expansion or contraction occurring
in the valve train.

The crankcase assembly consists of two reinforced aluminum alloy castings

divided at the centerline of the engine and fastened together by a series of body

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Section 72-00-01 IO-390-A Series Maintenance and Overhaul Manual

fit-through studs and bolts and nuts. The mating surfaces of the two castings are
joined without use of a gasket, and the main bearing bores are machined for the
use of precision-type main bearing inserts. The crankcase forms the bearings for
the camshaft.

The crankshaft is made from a chrome-nickel-molybdenum steel forging and all

journal surfaces are nitrided. A system of dynamic counterweights eliminates
torsional vibration.

An accessory housing is machined from an aluminum alloy casting and is

fastened to the rear of the crankcase and to the top of the oil sump. The two
magnetos and the gear-driven fuel pump are mounted on machined pads on the
accessory housing, and provisions for two additional accessories are provided.

Connecting rods are made in the form of “H” sections from alloy steel forgings.
They have replaceable bearing inserts in the crankshaft ends and split-type
bronze bushings in the piston ends. The bearing caps on the crankshaft ends of
the rods are retained by two bolts through each cap secured by nuts.

The pistons are machined from an aluminum alloy forging. The piston pin is of
the full-floating type with a plug at each end of the pin.

The lubrication system in the IO-390-A Series engine uses a wet sump. Figure
72-00-01-1 shows a schematic diagram of the oil system.

Oil Sump – The sump incorporates the usual oil drain plug, oil suction screen,
fuel injector mounting pad, and the conventional intake riser and intake pipe
connectors.

Cooling System – This engine is designed to be cooled by air pressure. Baffles

are provided to build up a pressure and force the air through the cylinder fins.
The air is then exhausted to the atmosphere through gills or augmenter tubes
usually located at the rear of the cowling.

Induction System – Lycoming IO-390-A Series engine is equipped with a

Precision Airmotive RSA type fuel injection system. The system is based on the
principle of measuring air flow and using the air flow signal in a stem type
regulator to convert the air force of the air into a corresponding fuel force. This
fuel force (fuel pressure differential) applied across the fuel metering section (jet
system) makes fuel flow proportional to air flow. A manual mixture control and
idle cut-off are provided. Particularly good distribution of the fuel-air mixture is
obtained through the center zone induction system, which is integral with the oil
sump and is submerged in the oil and aids in cooling the oil in the sump. From
the riser, distribution to each cylinder is by individual intake pipes. Fuel
vaporization takes place at the intake ports.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-01

Figure 72-00-01-1. Oil System Schematic Diagram

Lubrication System – The lubrication system is of the pressure wet sump type.
Figure 72-00-01-1 shows a schematic diagram of the oil system. The main
bearings, connecting rod bearings, camshaft bearings, valve tappets, push rods
and crankshaft idle gears are lubricated by means of oil collectors and spray. The
oil pump, which is located in the accessory housing, draws oil through a drilled
passage leading from the oil suction screen located in the sump. The oil from the
pump then enters a drilled passage in the accessory housing, where a flexible line
leads the oil to the external oil cooler. In the event that cold oil or an obstruction
should restrict the flow of oil to the cooler, an oil cooler bypass valve is
provided. Pressure oil from the cooler returns to a second threaded connection on
the accessory housing from which point a drilled passage conducts the oil to the
oil pressure screen, which is installed in a cast chamber located on the accessory
housing below the tachometer drive.

The oil pressure screen is provided to filter from the oil any solid particles that
may have passed through the suction screen in the sump. After being filtered in
the pressure screen chamber, the oil is fed through a drilled passage to the oil
relief valve, located in the upper right side of the crankcase in the front of the
accessory housing.

This relief valve regulates the engine oil pressure by allowing excessive oil to
return to the sump, while the balance of the pressure oil is fed to the main oil

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Section 72-00-01 IO-390-A1A6 Maintenance and Overhaul Manual

gallery, the oil is distributed by means of separate drilled passages to the main
bearings of the crankshaft. Separate passages from the rear main bearings supply
pressure oil to both crankshaft idler gears. Angular holes are drilled through the
main bearings to the rod journals. Oil from the main oil gallery also flows to the
cam and the valve gear passages, and is then conducted through branch passages
to the roller tappets and camshaft bearings. Oil enters the tappet through indexing
holes and travels out through the hollow push rods to the valve mechanism,
lubricating the valve rocker bearings and the valve stems. Residual oil from the
bearings, accessory drives and the rocker boxes is returned by gravity to the
sump.

The fuel injection system controls fuel flow in proportion to airflow with
injection.

Dual ignition is furnished by two Slick magnetos and harnesses.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-00-01

72-00-01b Engine Specifications

Table 72-00-01A. IO-390-A Series Engine Specifications

FAA Type Certificate E00006NY

Rated Maximum Continuous hp at rpm and Break-Specific Fuel Consumption (BSFC) 210 @ 2700
Performance Cruise (75% Rated) 158 @ 2450
Economy Cruise (60% Rated) 137 @ 2350
Fuel Consumption, Cruise, gph at 75% rated power 12.5 gal
60% rated power 9.1 gal
Propeller Drive Ratio 1:1
Propeller Shaft Rotation Clockwise
Bore (in.) 5.319
Stroke (in.) 4.375
Displacement (in.3) 389
Compression Ratio 8.9:1
Weight (lb) 315
Dimensions (in.): Height 19.35
Width 34.25
Length 30.70
Oil Sump Capacity (qt) 8
Fuel, Aviation Grade 100 or 100 LL
Fuel Injector, Precision Airmotive RSA-5AD1
Magneto Drive: Ratio to Crankshaft and Rotation 1.0:1 – Clockwise
Magnetos, (2) Slick, Retard – Left Model 4345
Slick, Plain – Right (or) Model 4370
TCM Left Model S4LN-200
TCM, Right Model S4LN-204
Tachometer Drive, Ratio to Crankshaft, and Rotation 0.5:1 –
Clockwise
Starter, Kelly Aerospace Geared - 12 Volt Standard*
24 Volt Optional
Alternator Drive, Ratio and Rotation 3.20:1 – Clockwise
Alternator, Kelly Aerospace - 12 Volt Optional*
24 Volt Optional
Accessory Drive, AND2000 Optional
Ratio to Crankshaft and Rotation 1.3:1 –
Counterclockwise
Propeller Governor Drive, AND20010, Type XX Optional
Ratio to Crankshaft and Rotation (Viewing Pad) .866:1 – Clockwise
Fuel Pump, Diaphragm Type Standard

Note: All locations and rotations are as viewed from the anti-propeller end of the engine.
* - For optional starters and alternators see the latest revision of Lycoming Service Instruction No. 1154.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-02

72-00-02 OPERATING INFORMATION

72-00-02a Pre-Start Checklist

Several items of maintenance must be performed before starting the engine for
the first flight of the day. The prestart inspection is intended as an overall check
to determine the general condition of the aircraft and the engine.

1. Check that all switches are in the “OFF” position.

2. Ensure that the magneto ground wires are securely connected.

3. Check the oil level.

4. Examine the fuel and oil line connections. Repair any leaks before the
aircraft is flown. Note any indications that may require further attention
during the 50-hour inspection.

5. Check all controls for general condition, travel, and freedom of operation.

6. Inspect and service the induction system air filter in accordance with the
airframe manufacturer’s recommendations.

Note: New, rebuilt, or newly overhauled engines and engines that have newly
installed cylinders must be inspected and serviced according to the
following schedule.

At 2-1/2 hours inspect the oil filter and oil screen contents (refer to
Section 05-20-02a).

At 25 hours, change oil and filter and inspect the filter and screens.

Thereafter, inspect at 50 hour intervals unless there are indications that

attention is required sooner.

72-00-02b Starting
The following are recommended starting procedures; however, the starting
characteristics of various airframe installations may necessitate some deviation
from these procedures. Refer to the Pilot’s Operating Handbook and the airframe
manufacturer’s maintenance manual for specific instructions.

Note: Cranking periods should be limited to 10 to 12 seconds with 5 minutes

rest between cranking periods.

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Section 72-00-02 IO-390-A1A6 Maintenance and Overhaul Manual

72-00-02b1 Cold Engine

1. Perform the prestart inspection.

2. Set the propeller governor to “FULL” rpm.

3. Turn the fuel valve to the “ON” position.

4. Open the throttle approximately ¼ inch.

5. Turn the boost pump on and move the mixture control to the “FULL RICH”
position until a slight but steady flow is indicated.

6. Return the mixture control to the “IDLE CUT-OFF” position; turn boost
pump off.

7. Set magneto selector switch. Consult airframe manufacturer’s handbook for

correct position

8. Engage the starter.

9. When the engine starts, place magneto selector switch in “Both” position.

10. Move mixture control slowly and smoothly to “FULL RICH”.

11. Check the oil pressure gage for indicated pressure. If oil pressure is not
indicated within 30 seconds, stop the engine and determine the trouble.

72-00-02b2 Hot Engine

Because fuel percolates and the system must be cleared of vapor, start a hot
engine using the same procedure as for a cold engine, above.

72-00-02b3 Cold Weather Starting

In extremely cold temperatures, oil congeals, battery capacity is lowered, and the
starter can be overworked. Proper preheating can facilitate cold weather starting
and to protect against abnormal engine wear, reduced performance, and
shortened time between overhauls.

Lycoming recommends preheat for cold weather starts and requires that preheat
be used when the engine has been allowed to cool down in temperature below
+10°F/-12°C.

Follow the procedures recommended by the airframe manufacturer and the

manufacturer of the preheat equipment being used to preheat the engine and oil.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-02

Caution

1. Be sure that the engine oil is in compliance with the recommended

grades (Refer to Table 72-50-01A).

2. Preheat carefully to avoid heat damage to non-metal parts. When

using hot air, open cowl flaps, if installed, to avoid damage from heat
build-up.

3. Do not exceed idle RPM until oil pressure is stabilized above the
minimum idling range. If oil pressure does not rise to the minimum
within 30 seconds, shut down the engine and investigate.

4. Do not take off if there are indications of:

a. Engine roughness

b. Low, high, or surging RPM

c. Low, high, or fluctuating oil pressure

d. Low or high fuel flow

e. Excessive manifold pressure.

72-00-02b4 Clearing A Flooded Engine

If the engine fails to start, assume that it is flooded. Use the following clearing
procedure then repeat the above starting procedure.

1. Turn the fuel boost pump off.

2. Place the mixture in “Idle Cut-Off”.

3. Select full throttle.

4. Use the starter to turn the engine over several times and clear fuel from the
cylinders.

Note: Cranking periods should be limited to 10 to 12 seconds with 5 minutes

rest between cranking periods.

5. Repeat the starting procedures.

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Section 72-00-02 IO-390-A1A6 Maintenance and Overhaul Manual

72-00-02b5 Ground Running and Warm-Up

The Lycoming IO-390-A1A6 engine utilizes air pressure to cool and thus
depends on the forward movement of the aircraft to maintain proper cooling.
When operating this engine on the ground, exercise care to avoid overheating.

1. Start the engine as outlined in the steps for starting a cold engine.

2. Head the aircraft into the wind.

3. Lean the mixture control during run up.

4. Operate the engine (while the aircraft is on the ground) with the propeller in
the minimum blade angle setting only.

5. Warm up at approximately 1000 to 1200 rpm.

Caution
Avoid prolonged idling and do not exceed 2200 rpm on the ground. The
engine is warm enough for take-off when the throttle can be opened
without the engine faltering.

72-00-02c Operations Checklist

1. Warm up as directed above.

2. Check both the oil pressure and oil temperature to ensure that they are both
within acceptable limits.

3. Leave the mixture control in the “FULL RICH” position.

4. Move the propeller control through its complete range to check operation and
return it to the “FULL LOW PITCH” position.

5. Check the magneto operation.

Note: Power output, propeller pitch, and mixture strength affect magneto drop-
off.

a. Set the propeller to minimum pitch angle.

b. Set the engine to produce 50 to 65% power as indicated by the manifold

pressure gage.

c. Set the mixture control to the “FULL RICH” position.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-02

Note: At these settings, the ignition system and spark plugs must work harder
because of the greater pressure within the cylinders. Under these
conditions, ignition problems, if any, will occur. Magneto checks at low
power settings will indicate only fuel/air distribution quality.

a. Switch from both magnetos to one and note the drop-off.

b. Return to both magnetos until the engine regains speed.

c. Switch to the other magneto and note the drop-off. The drop-off should
not exceed 50 rpm between magnetos. A smooth drop-off past normal is
usually a sign of a too lean or too rich mixture.

Note: Do not operate on a single magneto for too long a period. A few seconds
is usually sufficient to check drop-off and will minimize plug fouling.

72-00-02d Stopping and Shut-Down

1. If propeller is variable speed, set the propeller at minimum blade angle.

2. Idle until there is a decided decrease in cylinder head temperature.

3. Move mixture control to “IDLE CUT-OFF’.

4. When engine stops, turn ignition switch off.

Refer to Pilot’s Operating Handbook for additional information.

72-00-02e Operation Ground Check after Maintenance

1. Per the component manufacturer’s instructions, calibrate the cylinder head

temperature gage, oil temperature gage, oil pressure gage, manifold pressure
gage, and tachometer prior to testing.

Caution
Check that all vent and breather lines are properly installed and secured
as described in the airframe maintenance manual.

2. Install all intercylinder baffles, airframe baffles and cowling.

3. For optimum cooling during ground testing, use a test club. If a test club is
not available, the regular flight propeller may be used but the cylinder head
temperature must be closely monitored.

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Section 72-00-02 IO-390-A1A6 Maintenance and Overhaul Manual

4. Face the aircraft into the wind.

5. Start the engine as described in Section 72-00-02b.

a. Check the oil pressure gage for indicated pressure. If oil pressure is not
indicated within 30 seconds, stop the engine and determine the trouble.

b. If oil pressure indicated within 30 seconds, operate the engine at 1000

RPM until the oil temperature has stabilized or reached 140°F. After
warm-up the oil pressure cannot be less than the minimum pressure
stated in this manual.

c. Check the magnetos as follows:

i. (Controllable pitch propeller). With the propeller in minimum pitch

angle, set the engine to produce 50-65% power as indicated by the
manifold pressure gage unless otherwise specified in the aircraft
manufacturer’s manual. At these settings, the ignition system and
spark plugs must work harder because of the greater pressure within
the cylinders. Under these conditions, ignition problems can occur.
Magneto checks at low power settings will only indicate fuel/air
distribution quality.

ii. (Fixed pitch propeller). Aircraft that are equipped with fixed pitch
propellers, or not equipped with a manifold pressure gage, may
check magneto drop-off with the engine operating at approximately
1800 RPM (2000 RPM maximum).

iii. Switch from both magnetos to one and note drop-off; return to both
until engine regains speed and switch to the other magneto and note
drop-off, then return to both. Drop-off must not exceed 175 RPM
and must not exceed 50 RPM between magnetos. Smooth operation
of the engine but with a drop-off that exceeds the normal
specification of 175 RPM is usually a sign of propeller load
condition at a rich mixture. Proceed to step 5.c.iv.

iv. If the RPM drop exceeds 175 RPM, slowly lean the mixture until the
RPM peaks. Then retard the throttle to the RPM specified in step
5.c.i. or 5.c.ii. for the magneto check and repeat the check. If the
drop-off does not exceed 175 RPM, the difference between the
magneto does not exceed 50 RPM, and the engine is running
smoothly, then the ignition system is operating properly. Return the
mixture to full rich.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-02

d. Continue operation at 1000/1200 RPM for 15 minutes. Insure that the

cylinder head temperature, oil temperature, and oil pressure are within
the limits found in the Operation and Installation Manual, P/N 60297-34.
Shut the engine down and allow it to cool if necessary to complete this
portion of the test. If any malfunction is noted, determine the cause and
make the necessary correction before continuing the test.

e. Start the engine again and monitor oil pressure. Increase engine speed to
1500 RPM for a 5 minute period. Cycle propeller pitch and perform
feathering check as applicable per the airframe manufacturer’s
recommendations.

f. Run the engine to full-static airframe recommended power for a period of

no more than 10 seconds.

g. After operating the engine at full power, allow it to cool down

moderately. Check idle mixture adjustment prior to shutdown.

h. Inspect the engine for oil leaks.

i. Remove the oil suction screen and the oil pressure screen or filter to
determine any contamination. If no contamination is evident, then release
the aircraft for flight.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-03

72-00-03 TROUBLESHOOTING
Troubleshooting is the step-by-step procedure used to determine the cause for a
given problem and then selecting the best way to solve that problem.

72-00-03a General

1. Start by discussing the problem with the pilot and the facility management
people to assist you in narrowing the causes.

2. Review maintenance logs and use appropriate diagnostic tools to eliminate

simple and inexpensive solutions before proceeding to more complicated and
expensive remedies. Often a quick visual inspection of the engine will
provide evidence of obvious problems, such as intake and exhaust leaks,
physical damage to ignition harness, blocked breathers, gas and oil stains,
etc.

3. Consult the following Troubleshooting Chart as a diagnostic guide to the

most common and recurring problems, causes, and solutions. The chart
provides this information in a non-specific format. Proceed from the simplest
possible cause to the most complex.
Engine Troubleshooting Chart

Problem Cause Correction

Engine will not start or is hard to Defective battery Replace with a charged battery in
start. accordance with airframe manufacturer’s
instructions.

Incorrect starting procedure Refer to the engine operator’s manual or

the Airframe Flight Manual for the
recommended starting procedures.

Throttle valve open too far Set throttle control approximately ¼ inch
open for about 800 rpm.
Insufficient prime (may be Increase prime. Inspect priming system
accompanied by backfire) for leaks.

Flooded engine Turn ignition switch “on”and place the

(overpriming) mixture control in “Idle Cut-Off.” Fully
open throttle and crank the engine to
start. If the engine does not start in five
seconds, shut down and do not reattempt
to start until the starter cools down.
When the engine starts, retard the
throttle and advance the mixture slowly
to "Full Rich”.

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Section 72-00-03 IO-390-A1A6 Maintenance and Overhaul Manual

Problem Cause Correction

Engine will not start or is hard to Defective starter Replace starter.

start (cont.).

Lack of fuel Check fuel supply. Service as required.

Lack of fuel flow Disconnect fuel line and check fuel flow.
Inspect for evidence of leaks and correct
as required. Clean filters, strainers, lines,
or fuel valves.

Water in fuel injector Drain fuel injector and fuel lines.

Defective spark plug Remove plugs, inspect, clean, gap, test,

and replace as necessary.

Defective ignition wire Visually inspect ignition harness for

breaks and cracks. Remove distributor
cap from magneto and test leads using a
high-tension lead tester. Replace
defective wires.

Magneto improperly timed Time magnetos to engine. Refer to

to engine. section 72-60-03e.

Magneto internal timing Replace magneto with serviceable unit

not adjusted properly or and/or check internal timing of
“E” gap drifting because of magnetos. (Section 72-60-03e)
point or follower wear.

Rough Idle Incorrect idle mixture Adjust for proper mixture by turning the
scalloped wheel at the side of the
injector to either rich or lean condition
as appropriate (indicated by an arrow
and the letter “R” located on the injector
linkage). Readjust idle speed after
making mixture adjustments. Refer to
section 72-60-09e for complete
instructions.

Incorrect idle adjustment Adjust idle. Refer to section 72-60-09e.

Plugged fuel injector Locate affected cylinder by feeling for a
nozzles “cold” cylinder after a 2-minute period
of operation. Flow-check nozzles in
containers of equal size to locate
partially plugged nozzles. Refer to
section 73-10-01c for instructions. Clean
or replace nozzle. Clean nozzles in
Hoppe’s #9 gun cleaning solvent and
blow out with compressed air.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-03

Problem Cause Correction

Rough Idle (Cont.) Sticking valve in fuel flow Remove divider from engine and
divider disassemble (exercise caution not to
damage diaphragm during disassembly
or reassembly). Flush out foreign matter.
The divider valve’s seat may be hand-
lapped with a mild abrasive to remove
any burrs. Note: Fuel flow divider parts
are not interchangable. Never
interchange flow divider parts.

Nozzle screen and shroud Replace nozzle.

are deformed to extent that
it blocks or partially blocks
air bleed hole.

Leak in induction system Inspect flanges, gaskets and o-rings for

leaks and tighten as necessary. Inspect
for cracked intake pipes; replace as
necessary. Inspect for loose flange bolts
or loose plugs in intake port of cylinders;
torque as required. Inspect for fuel stain
evidence of leaking gaskets; replace
when found. Inspect for fuel drain valve
not properly seating.

Fuel vaporizing in lines and Operate with cowl flaps in the full open
flow divider (encountered position and keep ground operation to a
only at high ambient minimum. Operate with booster pump
temperatures and prolonged on as necessary.
operation at low or idle
rpm).

Internal injector leak Disconnect induction system at injector

inlet to observe impact tubes. Position
the throttle in the full “forward” position
and place the mixture in the full “rich”
position. Cap the fuel line to the flow
divider and turn on the boost pump. If
fuel is observed coming out of the
impact tubes, the injector has an internal
leak and must be replaced.

Cracked engine mounts or Replace in accordance with airframe and

defective mount bushings part manufacturer’s instructions.

Engine mount bushing Install in accordance with

improperly installed. manufacturer’s instructions.

August 2008 Page 17, Section 72-00

Section 72-00-03 IO-390-A1A6 Maintenance and Overhaul Manual

Problem Cause Correction

Rough Idle (Cont.) Fuel pressure too low Check for plugged fuel filter. Adjust fuel
(normal range for operation pressure. If necessary, replace fuel pump
14−45 psi). in accordance with section 72-60-04e.

Uneven cylinder Perform differential compression check.

compression Refer to section 72-30-02a. Do
boroscope inspection of low cylinders to
determine if further disassembly and
repairs are necessary. Refer to section
72-60-05.

Faulty ignition system Set engine power to 50−65% with

propeller in low pitch. Check both
magnetos for excessive dropoff and
ensure that not more than a 50 rpm
difference exists between mags. Note: A
smooth dropoff that exceeds limits may
indicate a lean or rich injector. Visually
check harness for physical damage.
Remove distributor block and check
leads using a high-tension lead tester.
Repair or replace components as
necessary. Remove plugs, inspect, clean,
gap, test, and replace as necessary.

Engine won’t idle unless boost Idle mixture is extremely Enrich idle mixture by turning scalloped
pump is on. lean. wheel at side of injector toward rich
condition (indicated by the arrow and the
letter “R” located on the injector
linkage). Readjust idle speed. Refer to
section 72-60-09e for complete
instructions.

Low fuel pressure Check for plugged fuel filter. Adjust fuel
pressure. If necessary, replace fuel pump
in accordance with section 72-60-04e.

Fuel vaporizing line Operate with cowl flaps in the full open
position and keep ground operation to a
minimum. Operate with boost pump on
as necessary.

Page 18, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-03

Problem Cause Correction

Engine won’t idle unless boost Pressure too low at idle Check for loose fuel fitting, tighten as
pump is on (cont.). speed (engine may also necessary.
lose fuel pressure as the
aircraft climbs).

Idle mixture is extremely This condition is indicated by excessive

rich. black exhaust. Correct by turning
scalloped wheel at the side of the
injector toward lean condition (turn
wheel away from the letter “R” located
on the injector linkage). Readjust idle
speed. Refer to section 72-60-09e for
complete instructions.

Engine pump fuel pressure Adjust fuel pump. If necessary, replace

is set too high. fuel pump in accordance with section
73-10-01b.

Boost pump pressure is set Adjust pressure. If necessary, replace

too high. pump in accordance with airframe
manufacturer’s instructions.

Poor idle cut-off Improper rigging of Adjust in accordance with airframe

mixture control linkage manufacturer’s instructions.

Mixture control valve is Remove mixture control assembly from

scored or not seating injector. Lap idle cut-off jet and valve
properly, or “O” ring on assembly on a good lap plate, using a
mixture jet is broken or mild abrasive, until all scores and burrs
deformed. are removed. Clean thoroughly and re-
assemble. Inspect the condition of the
“O”ring on mixture control jet. Check
for leaks by disconnecting fuel line at
the entrance to the flow divider. Place
throttle and mixture in “off” positions
and turn boost pump on. There should be
little or no fuel flow. More than 5cc per
minute indicates a leaking valve.

Vapor in lines Operate with cowl flaps in the full open

position and keep ground operation to a
minimum. Operate with boost pump on
as necessary.

Dirt is in the air bleed hole Remove and clean nozzles in Hoppe’s
of fuel injector nozzle. #9 gun cleaning solvent and blow out
with compressed air.

August 2008 Page 19, Section 72-00

Section 72-00-03 IO-390-A1A6 Maintenance and Overhaul Manual

Problem Cause Correction

Poor idle cut-off (cont.) Fuel jet in nozzles is Replace nozzles.

improperly located.

Valve in flow divider is Remove divider from engine and

sticking. disassemble (exercise caution not to
damage diaphragm during disassembly
or reassembly). Flush out foreign matter.
If necessary, replace the divider or have
it serviced at a vendor authorized
facility. Fuel flow divider parts are not
interchangable. Never interchange flow
divider parts.

Loose fuel line at flow Ensure main fuel line at flow divider and
divider or nozzle fuel injector are tight. Inspect all fuel
lines at divider and nozzles. Ensure fuel
nozzles are tight in the cylinders and are
not cross-threaded.

High fuel flow Plugged fuel injector Flow-check nozzles in containers of

nozzles indicated by high equal size to locate plugged nozzles.
flow reading on nozzle. Clean plugged nozzles in Hoppe’s #9
Pressure type gage only. gun cleaning solvent and blow out with
Not valid for direct flow compressed air.
type gage.

Faulty gage Install master fuel flow gage and run

engine to compare gages. Replace faulty
fuel flow gage.

ID of fuel lines is too small Check with a gage to verify fuel line ID
indicated by high flow is between 0.085−0.090 in. (do not mark
velocity on nozzle. inside of fuel line while measuring).
Pressure type gage only. Note: Primer lines have the same
Not valid for direct flow threaded connections as fuel lines but a
type gage. much smaller ID.

Injector rich Recalibrate and/or overhaul injectors

that are running rich at an approved
facility.

Low Fuel Flow Dirty fuel filter screen Remove and clean in acetone or MEK.
Blow out with compressed air.

Faulty gage Install master fuel flow gage and run

engine to compare gages. Replace faulty
fuel flow gage.

Page 20, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-03

Problem Cause Correction

Low Fuel Flow (Cont.) Flow divider does not open Disassemble, check for dirt and drag on
all the way (this may be diaphragm stem. Never interchange flow
intermittent). divider parts. They are flowed as an
assembly. Replace flow divider if
necessary.

Fuel line to fuel flow gage To detect broken or loose lines, inspect
is broken, loose, or for fuel dye stains. Disconnect line at
plugged. gage and injector and blow out with
compressed air to check for a plugged
line. Repair or replace line as necessary.

Low fuel pressure Adjust fuel pressure. Replace fuel pump

if necessary.

Injector lean Increases in cylinder head temperature,

EGT, or oil temperature indicate a lean
mixture. Run engine at a given power
setting full rich. Recalibrate and/or
overhaul injectors that are running lean
at an approved facility.

Engine will not turn static rpm or Tachometer reading is Verify tachometer operation. Have
will not develop rated rpm incorrect tachometer repaired or replaced; if
necessary.

Restriction in induction air Inspect and remove restriction. Verify

system. that airbox installation is in accordance
with airframe manufacturer’s installation
specifications.

Injector rich or lean Run engine at a given power setting full

rich. Recalibrate and/or overhaul
injectors that are out of specification at
an approved facility.

Propeller is out of Adjust in accordance with airframe

adjustment (not reaching manufacturer’s instructions.
specified low pitch).

Propeller governor is not Adjust in accordance with airframe

adjusted properly. manufacturer’s instructions.

August 2008 Page 21, Section 72-00

Section 72-00-03 IO-390-A1A6 Maintenance and Overhaul Manual

Problem Cause Correction

Engine will not turn static rpm or Muffler’s internal baffles Strike muffler with a rubber mallet or
will not develop rated rpm are broken and blocking the soft object and listen for a rattle. A rattle
(cont.) exhaust outlet. Note: indicates loose baffles. Remove muffler
Broken baffles are free to for thorough inspection. Replace as
move around in the necessary in accordance with airframe
muffler. The engine may manufacturer’s instructions.
turn static rpm’s
intermittently.

Excessively dirty air filter Replace in accordance with airframe

manufacturer’s instructions. Note:
Occasionally new filters will have an
excessive air drop through them. If this
condition is suspected, remove filter and
run engine to full throttle on a hard
surface in a dust-free area.

Incorrect magneto to Time magnetos to engine. Refer to

engine timing. section 72-60-03e.

Fouled spark plugs Remove and clean plugs.

Improper fuel flow Remove screens and flush out with

acetone or MEK. Blow out with
compressed air. Disconnect gage and
install a master fuel flow gage to
determine accuracy of aircraft fuel flow
gage. Replace injector as necessary.

Restriction in air inlet or Inspect air filters for cleanliness. Inspect

manifold induction system for breaks in ducting
that would allow foreign material or
heated air to enter induction system.
Repair or replace as applicable.

Improper fuel Consult section 73-00-01a.

Throttle lever not properly Adjust in accordance with airframe

adjusted manufacturer’s instructions.

Poor combustion Perform a differential compression

check. Refer to section 72-30-02a. Do
boroscope inspection to identify
excessively leaking valves, valve guides
or rings, and to locate any broken rings.
Perform top overhaul to correct
problems. Refer to section 72-60-05.

Page 22, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-03

Problem Cause Correction

Engine will not turn static rpm or Crankshaft to camshaft Note: The engine probably will turn up
will not develop rated rpm timing is off static rpm’s, but manifold pressure will
(cont.) be a little high. To vertify correct
crankshaft to camshaft timing, first
ensure all ignition and electrical switches
are “off”. Disconnect all spark plug
leads. Disconnect the starter. Remove
the top spark plug on #1 cylinder and
rocker box cover on #2 cylinder. Turn
engine to TDC on the compression
stroke on the #1 cylinder; observe that
when the piston in #1 cylinder goes over
TDC on compression, the intake valve in
the #2 cylinder is just starting to open
and the exhaust is just closing. If this
condition does not exist, the crankshaft
to camshaft timing is off. Remove
accessory housing and correct timing.
Refer to section 72-60-06e.

Engine Surges Fuel injector nozzles are Clean by flushing in Hoppe’s #9 gun
dirty cleaning solvent and blow out with
compressed air.

Low engine oil level Check oil level. Replenish as required.

Faulty propeller governor Test circuit.

circuit

Faulty governor Replace governor.

Incorrect propeller Verify that governor is the correct part

governor number.

Breather plugged Inspect and remove any obstructions

from breather.

Defective oil pump Repair or replace (erratic oil pressure

may be traced to the fact that the pump is
sucking air). Refer to section 72-60-04.

Propeller blades are Remove and overhaul propeller.

sticking in hub
intermittently.

Excessive front main Perform leak test. Refer to section 72-

bearing clearance 60-06e.

August 2008 Page 23, Section 72-00

Section 72-00-03 IO-390-A1A6 Maintenance and Overhaul Manual

Problem Cause Correction

Low oil pressure Insufficient oil Fill oil sump to proper level.

Pressure relief is out of Increase oil pressure by turning

adjustment. adjusting screw clockwise, and decrease
by turning counterclockwise.

Dirt or metal chips under Remove, disassemble, and clean.

oil pressure relief valve

Damaged oil pressure relief Replace or repair. Refer to section 72-

seat 60-06e.

High oil temperature Inspect the following areas for a cause:

1) proper oil level,
2) proper grade and weight of oil,
3) thermostatic bypass valve working
properly and seating squarely,
4) plugged or partially plugged oil
cooler lines or oil cooler,
5) excessive blowby,
6) air duct to cooler blocked or cooler
partially covered, and
7) defective temperature gage
Restriction at inlet side of Remove and clean oil suction screen and
oil pump oil passage to inlet side of oil pump.

Excessive internal spill-off Check the following areas for excessive

of oil oil flow, and repair or replace:
1) loose or missing plugs in oil galley,
2) piston cooling squirts blocked open
(accompanied by low oil pressure at
low or idle rpm),
3) excessive bearing clearance,and
4) cracked crankcase in area of oil
galley.
Air leak on suction side Check conditions of oil suction screen
gasket, oil sump gasket, and oil pump
mating surface to accessory housing.
Replace cracked or damaged parts.

Relocated oil pressure take- Use only the approved oil pressure take-
off point on the engine off point. Note: If the oil pressure take-
off point on the engine is moved closer
to the oil pump discharge, a rise in oil
pressure will be noted.

Page 24, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-03

Problem Cause Correction

Low oil pressure (cont.) Failed or failing bearings Excessive bearing wear may be
determined by the presence of metal in
the oil suction screen or oil filter.
Disassemble engine for inspection and
replacement of bearings.

High oil consumption Improper grade of oil Use only aviation-grade straight mineral-
type oil conforming to MIL-L-6082 or
SAEJ1966 specifications, or an aviation-
grade ashless dispersant type conforming
to MIL-22851 or SAEJ1899
specifications, as appropriate. Consult
the engine operator’s manual for
seasonal viscosity recommendations.
Failure of new rings to Use mineral oil for the first 50-100 hours
properly seat of operation before opting to change to
ashless dispersant oil. Climb to cruise
altitude at full power and operate at 75%
power for break-in.
Incorrectly installed piston Perform a differential compression
rings, worn piston rings, check. Refer to section 72-30-02. Do
glazed or excessively worn boroscope inspection (air leaking past
cylinder barrels rings can be detected by listening for a
hissing sound in the crankcase at the
breather entrance). Remove cylinders
and replace piston rings with new ones
and deglaze cylinder barrels. Refer to
section 72-60-05.
Worn valve guides Remove cylinders from engine and take
out valves. Measure guides for wear.
Replace guides worn out of limits. Refer
to section 72-60-05.
Oil leaks Inspect external area of engine for leaks
and repair same.
Oil being siphoned from Verify the oil filter cap is secure and that
engine in flight. the oil access door closes properly.
Verify that the breather hose is cut
properly and located to prevent
siphoning.
Oil level too high Do not fill above the maximum oil sump
capacity of 8 qt.

August 2008 Page 25, Section 72-00

Section 72-00-03 IO-390-A1A6 Maintenance and Overhaul Manual

Problem Cause Correction

High cylinder temperature Spark plugs of improper Install approved spark plugs.
heat rating were installed.

Cooling baffles missing, Verify that all baffles are installed

broken, or improperly properly and none are broken. Replace
installed. as necessary. Note: Never modify,
relocate, or elimate any cooling baffles.

Partially plugged fuel Flush with Hoppe’s #9 gun cleaning

nozzles solvent and blow out with compressed
air.

Fuel lines of improper ID Check with a gage to verify fuel line ID

being used is between 0.085−0.090 in. (do not mark
inside of fuel line while measuring).
Note: Primer lines have same threaded
connections as fuel lines but are of much
smaller ID.

Improper magneto to Verify magneto to engine timing is

engine timing synchronized at 25° BTDC. Note:
Timing advanced more than 25° BTDC
will cause the engine to run hotter. Time
magnetos to engine as necessary. Refer
to section 72-60-03.

Engine is operating Follow operator’s manual concerning

excessively lean. minimum fuel flows for various power
settings and never lean below minimum
fuel flows. Note: Check combustion
chamber for carbon deposits. The
absence of carbon deposits is indicative
of running the engine too lean.

Mixture control is Verify that full travel of the cockpit

improperly rigged. mixture control lever results in the
injector lever hitting the full rich and
idle cut-off stops.

High oil temperature Defective oil temperature Install master temperature gage and run
gage engine to compare gages. Replace faulty
gage.

Insufficient oil supply Check oil level at regular intervals and

maintain proper level.

Page 26, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-03

Problem Cause Correction

High oil temperature (cont.) Insufficient cooling air Verify the integrity of the air inlet and
outlet ducting to the oil cooler. Repair or
replace parts in accordance with airframe
manufacturer’s manual as necessary.

Improper grade of oil Use only aviation-grade straight mineral-

type oil conforming to MIL-L-6082 or
SAEJ1966 specifications, or an aviation-
grade ashless dispersant-type
conforming to MIL-22851 or SAEJ1899
specifications, as appropriate. Consult
the engine operator’s manual for
seasonal viscosity recommendations.

Oil cooler or oil cooler Remove oil cooler and oil cooler lines
lines are plugged or and flush out in accordance with
partially plugged. airframe manufacturer’s manual.

Thermostatic bypass valve Replace thermostatic bypass valve. Refer

is not operating properly or to section 72-60-04. Note: Also replace
seating squarely. filter base if valve is not seating
properly.

Excessive blow-by Perform a differential compression

check. Refer to section 72-30-02. Do
boroscope inspection for indications of
excessively worn or broken rings.
Perform top overhaul to correct
problems. Refer to section 72-60-05.

Leaks in engine induction Inspect and repair leaks.

system

High manifold pressure at idle Improperly adjusted fuel Adjust idle mixture to get a 25−50 rpm
injector rise when moving mixture control from
full rich to idle cut off. Readjust idle
speed after making mixture adjustments.
Refer to section 72-60-09e for complete
instructions.

Incorrect hydraulic lifters Replace with the correct part number for
were installed. lifters. Refer to section 72-60-05. Note:
Any time hydraulic lifters are removed
from the engine for cleaning and
inspection, keep the cylinders and
plungers together as an assembly. If they
become separated replace with new ones.
Arbitrarily assembled body and plunger
assemblies will change the leak-down
rate.

August 2008 Page 27, Section 72-00

Section 72-00-03 IO-390-A1A6 Maintenance and Overhaul Manual

Problem Cause Correction

High manifold pressure at idle Air leak in induction Inspect induction system for leaks and
(cont.) system repair as necessary. Note: Engine will
run rough at idle if induction system
leaks are present.
High oil pressure Oil pressure improperly Decrease oil pressure by turning oil
adjusted. pressure relief adjusting nut counter-
clockwise.
Improper weight of oil Use the recommended viscosity of oil
used. for the ambient temperature. Refer to the
engine operator’s manual.
Oil passage plugged from Remove pressure relief valve from the
pressure relief valve to engine and run a soft copper wire down
sump. through the oil passage to the sump to
clear blockage. Note: If blockage
persists remove sump and clear passage.
Relocated oil pressure Use only the approved oil pressure
takeoff point on the engine takeoff point. Note: If the oil pressure
takeoff point on the engine is moved
closer to the oil pump discharge, a rise in
oil pressure will be noted.

Oil temperature is too cold. Allow oil temperature to increase before

increasing throttle.

Page 28, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-04

72-00-04 ENGINE REMOVAL

Remove the propeller and cowling following the airframe manufacturer’s
procedures.

Note: During removal/disassembly, tag and mark ports, clips, tubes, wires, etc.,
to prevent improper installation/assembly.

72-00-04a Disconnecting the Engine

1. Remove the oil drain plug from the sump and drain the oil from the engine.

2. Replace the oil drain plug.

3. Disconnect and cap the fuel supply line.

Caution
Dispose of the used oil and clean up any spilled oil or fuel in compliance
with federal, state, and local environmental regulations.

4. Disconnect any relays, gages, or other indicating devices following the

airframe manufacturer’s procedures.

5. During removal of tubes or engine parts, look for indications of scoring,

burning or other undesirable conditions. To facilitate reinstallation, observe
the location of each part during removal. Tag unserviceable parts and units
for investigation and possible repair.

6. Extreme care must be taken to prevent dust, dirt, lockwire, nuts, washers or
other foreign matter from entering the engine. Suitable plugs, caps, and other
covering must be used to protect all openings as they are exposed. Dust caps
must be installed over, not in, tube ends. Flow through the lines may be
blocked if lines are inadvertently installed with dust caps in the tubes.

7. If at any time items are dropped into the engine, the assembly process must
stop until the dropped articles are located, even though this may require a
considerable amount of time and labor. Before assembling or installing any
part, be sure it is thoroughly clean.

8. Replace all gaskets, packings, and rubber parts at reassembly. Make sure the
new nonmetallic parts to be installed (such as an oil seal) show no sign of
having deteriorated in storage.

August 2008 Page 29, Section 72-00

Section 72-00-04 IO-390-A1A6 Maintenance and Overhaul Manual

9. Lockwire, lockwashers, tablocks, tabwashers, or cotterpins must never be

reused. All lockwire and cotterpins must fit snugly in holes drilled in studs
and bolts for locking purposes. Install a cotterpin so that the head fits into the
castellation of the nut, and, unless otherwise specified, bend one end of the
pin back over the stud or bolt and the other end down flat against the nut.
Use only lockwire and cotterpins made of corrosion resistant steel. Bushing
plugs must be lockwired to the assembly boss or case. Do not lockwire the
plug to the bushing.

10. To protect critical areas of engine parts against scratches and nicks, tool
surfaces contacting these areas must be covered with protective material.

11. During replacement of components, note condition of any removed

preformed packings. Pieces accidentally torn or cut from packings must be
retrieved, regardless of size, even if this entails a systematic disassembly and
cleaning of the system. Make sure that new packings are free of cuts,
flashings and deformities which may be sheared off at installation.

12. When installing engine parts that require the use of a hammer to facilitate
assembly of installation, use only a plastic or rawhide hammer.

13. Whenever adhesive tape has been applied to any part, the tape must be
removed and the part thoroughly cleaned of all tape residue prior to being
subjected to high temperature during engine run. Do not leave tape or tape
residue on engine parts.

14. If any part has been coated with corrosion preventive compounds, all traces
of this compound and accumulated foreign matter must be removed.

72-00-04b Removing External Accessories

Consult the airframe manufacturer’s instructions to disconnect any accessory
connections or to remove any external accessories that might interfere with the
removal of the engine from the airframe. Refer to Section 72-60-04.

72-00-04c Lifting

1. Refer to Figure 72-00-04-1.

2. Attach an engine-lifting cable with a minimum capacity of 750 lbs. to the

lifting lugs on the engine.

Page 30, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-04

Figure 72-00-04-1. Lifting Lugs and Engine Mounts

3. Using a crane or overhead hoist able to support a minimum weight of 750 lb,
take up any slack in the lifting cable until it is taut enough to support the
weight of the engine.

4. Remove the nuts and bolts from the engine mounts supplied by the airframe
manufacturer.

Note: Do not remove the engine-mounting brackets from the engine. They
serve as tie down points used when the engine is crated or packed for
shipment. They are also needed to mount the engine in an overhaul stand
in an overhaul facility.

5. Lift the engine from the airframe.

August 2008 Page 31, Section 72-00

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Page 32, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-06

72-00-05 LONG-TERM PRESERVATION

Engines in aircraft that are flown only occasionally may not achieve normal
service life because of corrosion. This occurs when moisture from the air and
products of combustion combine to attack cylinder walls and bearing surfaces
during periods when the aircraft is not used. The procedures for combating this
condition consists of coating the vulnerable surfaces with rust inhibitive
compounds as herein described.

Note: Need for preservation must be evaluated by the owner or operator of the
aircraft based on environmental conditions and frequency of aircraft
activity. The time periods given are recommendations based on normal
conditions.

Our experience has shown that in regions of high humidity, active corrosion can
be found on cylinder walls of new engines inoperative for periods as brief as two
days. In engines that have accumulated 50 hours or more time in service in a
short period, the cylinder walls will have acquired a varnish that tends to protect
them from corrosive action; such engines under favorable atmospheric conditions
can remain inactive for several weeks without evidence of damage by corrosion.

Aircraft operated close to oceans, lakes, rivers and humid regions have a greater
need for engine preservation than engines operated in arid regions.

72-00-05a Active Engines

Engine temperature and length of operating time are very important in
controlling rust and corrosion. The desired flight time for air cooled engines is at
least one continuous hour at oil temperatures of 165°F to 200°F at intervals not to
exceed 30 days, depending on location and storage conditions. This one hour
does not include taxi, take-off and landing time. If recommended oil temperatures
are not obtainable, contact aircraft manufacturer for availability of oil cooler
winterization plates.

The aircraft temperature gages should be checked to make sure that they are
accurate.

The cooling air baffles need to be in good condition and fitted properly to assure
proper cooling air flow.

The oil cooler system needs to be of the proper size for the engine and airframe
installation. Oil coolers that are sized incorrectly can cause over-heating or below
minimum temperatures. Low temperatures are just as harmful as high
temperatures due to build-up of water and acids.

August 2008 Page 33, Section 72-00

Section 72-00-06 IO-390-A1A6 Maintenance and Overhaul Manual

Oil changes are very important in minimizing rust and corrosion. Refer to section
72-50-01d for recommended oil/filter change intervals and procedures.

Pulling engines through by hand when the aircraft is not run or flown for a week
or so is not recommended. Pulling the engine through by hand prior to start or to
minimize rust and corrosion does more harm than good. The cylinder walls,
piston, rings, cam and cam follower only receive splash and vapor lubrication.
When the prop is pulled through by hand, the rings wipe oil from cylinder walls.
The cam load created by the valve train wipes oil off the cam and followers.
After two or three times of pulling the engine through by hand without engine
starts, the cylinders, cam and followers are left without a proper oil film. Starting
engines without proper lubrication can cause scuffing and scoring of parts
resulting in excessive wear.

72-00-05b Inactive Engines

If it is known that an aircraft is to remain inactive for 30 or more days, the
following procedure should be applied to the engine, especially if the aircraft is
located near salt water or similar humid environment.

1. Install a preservative by one of the following methods:

a. Drain the lubricating oil from the sump or system and replace with a
preservative oil mixture. This preservation mixture consists of one part
by volume MIL-C-6529C Type 1 concentrated preservative compound
added to three parts by volume of MIL-L-6082C (SAE J1966), Grade
1100 mineral aircraft engine oil or oil conforming to MIL-C-6529C Type
II. Follow carefully the manufacturer’s instructions before use.

b. An alternative method is the use of Cortec VC1-326 preservative

concentrate added to the original oil at a ratio of 1 part VC1-326 to 10
parts of oil.

2. Operate the engine until normal temperatures are obtained.

Do not stop engine until oil temperature has attained 180°F (82°C). If
weather conditions are below freezing, oil temperature should reach at least
165°F (73°C) before shut down.

3. Remove sufficient cowling to gain access to the top spark plugs and remove
them.

4. Through the spark plug hole, spray the interior of each cylinder with
approximately two ounces of the preservative oil mixture using an airless
spray gun (Spraying Systems Co., Gunjet Model 24A-8395 or equivalent). In
the event an airless spray gun is not available, a moisture trap may be
installed in the air line of a conventional spray gun.

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5. Reinstall spark plugs and do not turn crankshaft after cylinders have been
sprayed.
Note: Oils of the type mentioned are to be used in Lycoming aircraft engines
for preservation only and not for lubrication. See section 72-50-01a for
recommended lubricating oil.

6. If the aircraft is stored in a region of high humidity, or near a sea coast it is

better to use dehydrator plugs instead of merely replacing the spark plugs as
directed in the preceding step. Cylinder dehydrator plugs, MS-27512-2 or
equivalent may be used.

7. Preferably before the engine has cooled, install small bags of desiccant in
exhaust and intake ports and seal with moisture impervious material and
pressure sensitive tape. Any other opening from the engine to the
atmosphere, such as the breather, and any pad from which an accessory is
removed, should likewise be sealed.

8. Firmly attach red cloth streamers to any desiccant bags installed in the intake
and exhaust passages to insure material is removed when the engine is made
ready for flight. Streamer should be visible from outside the aircraft.
Propeller should be tagged, “Engine preserved – do not turn propeller”.

9. At 15-day maximum intervals, a periodic check should be made of the

cylinder dehydrator plugs and desiccant. When the color of the desiccant has
turned from blue to pink the preservation procedure must be repeated.

10. To return the aircraft to service, remove seals, tape, and desiccant bags. Use a
solvent to remove type residue. Remove spark plugs or dehydrator plugs.
With the magnetos off rotate the propeller by hand through sufficient rotation
to remove excessive preservative oil from the cylinders. Drain the remaining
preservative from the engine through the sump.

Warning
To prevent serious bodily injury or death, before moving the propeller
take all precautions to prevent the firing of the engine. Disconnect spark
plug leads; insure magnetos are switched off and P-leads are grounded;
insure that the throttle is closed and the mixture is in “Idle Cut-Off”. Do
not stand within the arc of the blade. Even without spark, compression
can cause the propeller to move with sufficient force to cause serious
injury.

Install spark plugs and reconnect all parts in accordance with manufacturer’s
instructions. Service the engine with approved lubricating oil.

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Section 72-00-06 IO-390-A1A6 Maintenance and Overhaul Manual

Note: Although the above procedures should prevent corrosion under favorable
conditions, it is recommended that the engine be periodically inspected
for evidence of corrosion.

The forgoing are general recommendations for proper engine care. Since local
conditions may differ and Lycoming has no control over the application of these
recommendations, no warranty against corrosion is intended.

Note: Cortec Corp. – manufactures preservative oils

4119 White Bear Parkway
St. Paul, MN 55510
Phone: 612-429-1100
800-4-CPORTEC
Fax: 612-429-1122

Protect Air Mfgs. – MS27512-2 Plugs

Fernandina Beach, FL 32034

72-00-05c Fuel Injector Preservation

Caution
At all times, exercise care to prevent engine oil or fuel from entering the
air section of the fuel injection servo.

To ensure maximum protection, the following measures must be observed:

1. The fuel section must be adequately protected to inhibit deterioration of

rubber parts.

2. The air section must be protected to prevent entrance contamination.

3. The exterior must be protected to avoid corrosion or physical damage from

environmental issues such as dust, dirt, or moisture.

For 28-day Or Longer Preservation

Any unit removed from service for a period of 28 days or longer must be flushed
with preserving oil. Any good grade of clean #10 oil is satisfactory. For
preservation, perform the following steps:

1. Remove plugs and/or caps from fuel ports and drain all residual fuel.

2. Replace all plugs and caps except those for fuel inlet and outlet.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-06

3. Introduce #10 oil from a filtered source (10 micron) into the fuel inlet by
gravity pressure only until oil flows from the outlet port.

4. Drain oil from the unit. A film of oil on internal parts of fuel section is
sufficient to preserve the servo.

5. Replace plugs and/or caps in fuel inlet and outlet.

Special Consideration For Storing Near Salt Water

If units are to be stored near or shipped over salt water, the following precautions
must be observed:

1. Spray external surface of unit with clean grade #10 oil.

2. Pack each unit in a clean, dust-proof container with one-half pound (0.091
kg) bag of silica gel crystals. The silicon gel crystals must not come in
contact with the unit. Wrap container with moisture-proof material and seal.
Pack unit in a suitable shipping case.

72-00-05d Factory Engine Preservation

New, rebuilt, and overhauled engines are preserved for either 60 or 180 days.
The date of preservation is the date printed on the sticker on the outside corner of
the engine box with the gross weight; or it may be written on the top of the box
following a “Preservation Date” stamp. The preservation date is intended to
protect the engine from corrosion for the specified time interval. It is not
intended to protect the engine indefinitely.

Note: Corrosion is warrantable only during the specified preservation period.

Perform the following steps at the end of the preservation period when keeping
an engine in storage.

For 60-day Factory Preservation

After the first 60 days, and every 60 days thereafter, perform the following steps:

1. Remove the top and bottom spark plugs from the cylinder to be inspected.

2. Rotate the crankshaft until the piston is at bottom dead center.

3. Using a 4x boroscope with a 70° angle of view or similar equivalent internal

examining device, check each cylinder for evidence of corrosion.

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Note: Do not rotate the engine while conducting the boroscope evaluation.

Note: The diameter of the boroscope must be smaller than the diameter of the
spark plug hole.

4. Repeat steps 1. thru 3. until each cylinder is inspected. Reinstall the spark
plug.

5. Remove the rocker box covers and visually inspect for any evidence of
corrosion. When the inspection is finished, reinstall the rocker box covers.

6. Remove the accessories and visually inspect the drives and shafts to ensure
that no moisture or corrosion is evident. When the inspection is finished,
reinstall the accessories.

7. After the first sign of corrosion contact a Lycoming distributor or Lycoming

Technical Service at 877-839-7878 (877-TEX-SUPT).

After a period of one (1) year from the preservation date, the engine must be
placed in service or the above steps 1. thru 6. must be performed as directed. As
previously stated, corrosion is warrantable only during the specified preservation
period. Performing the above steps does not extend the corrosion warranty.

For 180-day Factory Preservation

Caution
Do not disturb the clear plastic bag in which the engine is sealed.

After the first 180 days, and every 60 days thereafter, perform the following
steps. Note that to perform these steps it will be necessary to remove some of the
engine packaging.

1. Remove the top foam pillow. Instructions for the removal are located on a
sticker on the outside of the engine box.

Note: Do not remove the engine from the box.

Note: Do not disturb the clear plastic bag in which the engine is sealed.

2. Inspect the moisture indicator. The indicator is resting on top of the cylinders
on one side of the engine and is visible through the bag. If moisture is
present, the indicator will have turned from blue to pink.

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Note: If the moisture indicator has turned from blue to pink then the engine
must be inspected using steps 1. thru 7. listed under 60 day preservation.

3. Inspect the clear plastic engine bag to be sure there are no visible signs of
damage. Damage to the container could cause the preservation to be lost.

Note: If the bag is found to be torn or damaged, then the engine must be
inspected using steps 1. thru 2. listed under 60 day preservation.

4. At the end of 180 days, if the moisture indicator shows no signs of moisture
and the plastic bag is neither torn nor damaged, the preservation may be
extended 60 days. As long as no moisture is indicated or the bag is not
damaged, the preservation can be extended in 60 days intervals for up to one
year from the preservation date on the box.

5. After a period of one (1) year from the preservation date, the engine must
either be placed in service or the above steps 1. thru 3. must be performed as
directed. As previously stated, corrosion is warrantable only during the
specified preservation period. Performing the above steps does not extend the
corrosion warranty.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-00-06

72-00-06 ENGINE INSTALLATION

Each Lycoming engine undergoes a thorough preservative treatment before

leaving the factory. To protect the cylinders and related parts, preservative oil is
sprayed into each cylinder. Careful uncrating and uninhibiting of the engine is
very important to prevent any of the preservative oil from entering the induction
system.

72-00-06a Uncrating

The Lycoming IO-390-A Series engine has been carefully packed for shipment to
prevent damage in transit and to ensure that the engine reaches its destination in
perfect condition.

Note: Any engine that has been stored in a cold area must be brought into an
area with a temperature of at least 70°F (21°C) for 24 hours before
uncrating. If this is not possible, the preservative oil in the engine must
be warmed to facilitate draining by heating the cylinders with heat lamps.

3. Remove the top of the crate and set it aside.

4. Lift and set aside any packing materials from on top of the engine.

5. Connect an engine-lifting cable to a winch, hoist, or crane able to support a

minimum load of 750 lb.

6. Connect the engine-lifting cable to the lifting lugs on the top of the engine.

7. Lift the engine from the crate.

72-00-06b Uninhibiting

72-00-06b1 Engine

Caution
Do not rotate the crankshaft of an engine containing preservative oil
before removing the bottom spark plugs. Engine damage will result.

Caution
Avoid contact of preservation oil with painted surfaces. If preservation
oil does contact a painted surface, clean it off with a solvent as soon as
possible.

8. Remove all the bottom spark plugs.

Revised June 2009 Page 41, Section 72-00

Section 72-00-06 IO-390-A1A6 Maintenance and Overhaul Manual

2. Turn the crankshaft three or four revolutions by hand.

3. Tilt the engine to one side until the spark plug holes on that side are oriented
vertically.

4. Rotate the crankshaft at least two revolutions and allow the oil to drain out
through the spark plug holes.

5. Repeat steps 3. and 4. for the opposite side of the engine.

6. Inspect the spark plugs before reinstalling them. If they are not clean, wash
them in clean oil-based solvent. Dry them with compressed air.

7. Remove the oil sump plug and allow any preservative oil that has
accumulated in the sump to drain.

8. Remove the oil screen and clean it with a hydrocarbon-based solvent such as
Varsol or equivalent.

9. Reinstall the oil screen.

10. If a constant speed propeller is to be used, the expansion plug must be

removed from the crankshaft. Pierce a 1/8 in. to 3/16 in. hole in the center of
the plug to remove it.

11. Replace the oil sump plug and install a safety wire. Refer to section 70-00-02
for lockwire information.

12. Fill the sump with 8 quarts of aviation-grade oil. Refer to section 72-50-01a
for oil recommendations.

13. Inspect the induction riser to ensure that it is clean and dry. If a significant
amount of preservative oil is noted, clean, reinspect, and reinstall the intake
pipes.

72-00-06c Fuel Injector

Caution

Do not immerse or stand servo unit in fluid of any kind.

1. With the fuel outlet port uncapped, apply flushing fluid (Naptha, Stoddard
Calibration Fluid conforming to MIL-C-7024D Type II, or equivalent) to
inlet port. Do not exceed an inlet pressure of 15 psi (103.43 kPa).

2. Remove the fuel inlet strainer and clean it with a hydrocarbon based solvent
such as Varsol or equivalent. Refer to section 73-20-01a.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-06

3. Inspect the fuel supply lines, fuel manifold, throttle body, and “bullet nose”
venturi to ensure they are clean and dry.

Caution
Dispose of used engine preservative and solvents in accordance with all
applicable federal, state, and local environmental regulations.

Note: If a small amount of preservative oil remains in the engine, it will not be
harmful; however, during the 25-hour inspection, the oil should be
drained while the engine is hot. This will remove any residual
preservative oil.

72-00-06d Installing the Engine

1. If the engine is to be installed in an airframe from which an engine has

previously been removed, inspect the engine mounts to ensure they are not
bent, misaligned, distorted, or damaged.

Caution
Distorted, misaligned, bent, or damaged engine mounts may cause
engine or airframe damage or engine failure.

2. Refer to the airframe manufacturer’s instructions for attaching the engine to

the engine mounts.

72-00-06e Connecting External Accessories

1. Accessory Drive: An accessory drive pad is provided for a customer

installed accessory. Accessory Drive Pad No. 1 will accept an accessory with
mounting flange and spline compatible with AND20000. Accessory Drive
Pad No. 2 will accept an accessory with mounting flange and spline
compatible with AND20000 or AND20001.

a. Remove cover plate and gasket.

b. When installing the accessory, use the gasket and hardware specified by
the airframe manufacturer.

c. Torque to the value specified for the thread size in the Table of Limits.

2. Alternator: An alternator mounting pad is provided on the bottom of the

crankcase. For optional alternators see the latest revision of Service
Instruction No. 1154. Refer to Lycoming Parts Catalog P/N PC-409-1 for a
listing of the mounting hardware.

August 2008 Page 43, Section 72-00

Section 72-00-06 IO-390-A Series Maintenance and Overhaul Manual

a. The alternator blast tube must be connected to a source of cooling air

sufficient to prevent alternator temperature from exceeding maximum
limits.

i. Alternator Stator Slot - 360°F

ii. Stator End Turns - 360°F

iii. Drive End Bearings - 248°F

iv. Positive Head Sink - 305°F

b. Torque to the value specified for the thread size in the Table of Limits.

3. Propeller Governor: A propeller governor drive pad compatible with

AND20010 Type XX is provided on the upper left front of the crankcase.

a. Remove cover plate and gasket.

b. When installing the propeller governor, use the gasket and hardware
specified by the airframe manufacturer.

c. Torque to the value specified for thread size in Table 72-00-06A.

3. Connect oil and fuel supply lines and any reporting devices, sensors, and
senders per the airframe manufacturer’s instructions.
Table 72-00-06A. Accessory Drive

Maximum
Maximum Torque Overhang
Accessory Location Thread Moment
Size Continuous Static
(in.-lb.) (in.-lb.) (in.-lb.)
Accessory Pad 1 Upper Right Side of ¼-20 70 450 25
Accessory Housing
Prop. Governor Lower Right Side of ¼-20 120 1200 40
Accessory Housing
Prop. Gov. Pad Upper Left Front of 5/16-18 125 1200 40
Crankcase
Alternator Bottom 5/16-18 60 120 175

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-06

72-00-06f Pre-Oiling Engines Prior to Start

Caution
To eliminate the possibility of high-speed bearing failure resulting from
insufficient lubrication during initial starts, all aircraft engines must be
pre-oiled after an overhaul, following oil cooler draining or replacement,
or whenever the oil lines have been disconnected.

Warning
If a propeller is installed, remain clear of the propeller turning arc. The
propeller will turn during this procedure, and could cause injury.

1. Fill the oil cooler with oil.

2. Remove one spark plug from each cylinder of the engine.

3. If the aircraft is not equipped with an oil pressure gage, remove the STD-
1102 allen plug from the upper left front of the main galley.

4. Place the mixture control lever in the “IDLE CUT-OFF” position and the
fuel selector switch in the “OFF” position.

5. Turn the engine with the starter (or with an external power source, if
available) until a minimum oil pressure of 20 lb. is indicated on the oil
pressure gage or until there is a steady flow of oil from the opening on the
engine.

Note: Cranking periods should be limited to 10 to 12 seconds with 5 minutes

rest between cranking periods.

Caution
If there is no indication of steady oil pressure after five attempts, the
cause should be determined and fixed.

6. Turn the starter for an additional 10 seconds to verify that the oil pressure
remains at 20 lb.

7. Reinstall the spark plugs and proceed with normal starting procedures
immediately. Refer to section 72-00-02b.

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Section 72-00-06 IO-390-A1A6 Maintenance and Overhaul Manual

8. When the engine starts, observe the oil pressure gage. If there is no oil
pressure indication, shut down the engine until cause is determined.

9. Allow the engine to run for approximately 3 minutes at 1000 rpm.

10. Shut down in accordance with section 72-00-02d.

Page 46, Section 72-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-07

72-00-07 ENGINE ORDERING AND RETURN

Some aircraft owners may choose to order a new or rebuilt exchange replacement
engine to minimize the time period their aircraft is grounded during engine
overhaul.

72-00-07a Engine Ordering

The following information must be provided with the engine order to the
authorized Lycoming distributor to ensure that the correct replacement engine is
shipped in a timely fashion.

1. Serial number of the engine being replaced.

2. Model of engine.

3. Total time on the engine being replaced.

4. Condition of the engine being returned.

a. Normal runout.

b. Failure.

c. Accident involvement.

Example of an Engine Order

Engine serial number L-12345-67A

Model number IO-390-A1A6
Total time (hr) 2000
Condition Normal runout

72-00-07b Return of Runout Engines

Rebuilt engines are sold on an exchange basis only, and an operable engine or a
carcass of a like model engine must be returned to Lycoming within 45 days of
the engine order. The Exchange Engine Tab (Form 156C-5M-76) listing the
applicable data and all engine log books must accompany the engine.

If the exchange engine is to be credited against a transaction older than two

years, a copy of the invoice must be included with the engine being returned.
Deviating from this policy is permissible only when an outright rebuilt engine
sale is approved in advance by authorized factory personnel. Factory-new
engines may always be purchased on an outright basis.

August 2008 Page 47, Section 72-00

Section 72-00-07 IO-390-A1A6 Maintenance and Overhaul Manual

72-00-07c Return of Engines for Special Adjustment Consideration

Engines that are returned by the distributor for warranty work or for special
adjustment must be accompanied by the following information.

1. All engine logbooks.

2. Spark plugs.

3. All accessories including the fuel injector servo.

4. Magnetos and ignition harnesses.

All items must be returned in “as is” condition to fully evaluate the engine
problem.

Note: If all of the above information is not furnished with the engine, no
warranty investigation will be made and the engine will be accepted for
exchange credit only.

Engines that are being returned must be properly preserved against corrosion
prior to shipment. Engines being returned from outside the United States must be
shipped through a consolidation point, where the engines could be delayed in
shipping; thorough preservation is critical.

Upon receipt and inspection of a failed engine in the factory, an appropriate

credit against the invoice for a replacement engine will be issued. This credit will
be based on the provisions outlined in the Published Warranty for new, rebuilt,
and overhauled reciprocating engines. In cases where prorate credit is applicable,
the credit will be based on a cost-per-hour basis. The formula used to determine
the cost per hour is computed by dividing the exchange price by the time
between overhaul (TBO) hours.

Your complete cooperation will enable Lycoming to provide the correct model
replacement engine and to continue providing service in a timely manner.

72-00-07d Parts Return⎯International

Parts being returned to Lycoming from distributors outside the United States
must use the following procedure.

1. Complete a Warranty Application and Return Material Form 916 or a

Request for Instant Credit Form TLRED-1091.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-00-07

2. Send the original copy of the appropriate form via first class mail to the
address below.

3. Include copy number 5 of the selected form packaged with the part or parts
being returned for warranty consideration.

4. Securely package and properly preserve parts being returned as required to

prevent additional damage from shipping.

5. Return the parts with all transportation, duty and handling charges prepaid to:

Lycoming Engines
Warranty Department
652 Oliver Street
Williamsport PA 17701

Note: Do not address the shipment to the attention of any individual. This will
cause unnecessary delays.

Note: Any parts having a value of less than $100.00 distributor net need not be
returned unless their return is required by a service publication.

Note: Do not return parts for warranty consideration via the consolidation
points. Consolidation points are expressly for the return of engine cores.
Parts and/or engines returned for warranty consideration via
consolidation points are subject to delay or damage.

Note: Parts must be returned to Lycoming within 45 days from the date of
occurrence or the warranty will not be honored.

Note: Parts received without the proper form will be returned to the distributor
freight collect.

72-00-07e Parts Return⎯Domestic

Parts being returned to Lycoming from distributors within the United States must
use the following procedure.

1. Complete a Warranty Application and Return Material Form 916 or a

Request for Instant Credit Form TLRED-1091.

2. Send the original copy of the appropriate form via first class mail to the
address below.

3. Include copy number 5 for the selected form packaged with the part or parts
being returned for warranty consideration.

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Section 72-00-07 IO-390-A1A6 Maintenance and Overhaul Manual

4. Securely package and properly preserve parts being returned as required to

prevent additional damage from shipping.

5. Return the parts with all transportation, duty, and handling charges prepaid
to:

Lycoming Engines
Warranty Department
652 Oliver Street
Williamsport, PA 17701

Note: Do not address the shipment to the attention of any individual. This will
cause unnecessary delays.

Note: Any parts having a value of less than $100.00 distributor net need not be
returned unless required by a service publication.

Note: Do not return parts for warranty consideration via the consolidation
points. Consolidation points are expressly for the return of engine cores.
Parts and/or engines returned for warranty consideration via
consolidation points are subject to delay or damage.

Note: Parts must be returned to Lycoming within 30 days from the date of
occurrence or the warranty will not be honored.

Note: Parts received without the proper form will be returned to the distributor
freight collect.

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IO-390-A1A6 Maintenance Manual Section 72-20-00

72-20-00 POWER SECTION MAINTENANCE

72-20-01 GENERAL INFORMATION
The power section of this engine consists of the crankcase, the crankshaft and
counterweights, the camshaft, and the bearings.

72-20-02 CRANKCASE
There are no regularly scheduled maintenance procedures that apply to the
crankcase.

72-20-03 CRANKSHAFT AND COUNTERWEIGHTS

There are no regularly scheduled maintenance procedures that apply to the
crankshaft and counterweights.

72-20-04 CAMSHAFT
There are no regularly scheduled maintenance procedures that apply to the
camshaft.

72-20-05 BEARINGS
There are no regularly scheduled procedures that apply to the bearings.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-30-01

72-30-00 CYLINDER SECTION MAINTENANCE

72-30-01 GENERAL INFORMATION
The cylinder section of this engine consists of the cylinders, rings, pistons, push
rods, valves and valve springs, and hydraulic tappets.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-30-02

72-30-02 CYLINDERS
Regularly scheduled maintenance for the cylinders consists of compression
checks and cylinder removal and replacement, and valve check.

72-30-02a Compression Check

9. Perform compression checks at 100 hours of engine operation and annual

inspection intervals. A compression check is also recommended any time
loss of power, increasing oil consumption, hard starting, or other evidence of
unexplained abnormal operation is encountered.

10. Record the results in the engine maintenance logs to determine progressive
wear trends.

Figure 72-30-02-1. Typical Differential Compression-Measuring Device

72-30-02a1 Differential Compression Test Equipment Specifications

Differential compression testers acceptable for use with the IO-390-A Series will
incorporate a 0.250 in. long restrictor orifice with a 0.040 in. ID (No. 60 drill)
orifice diameter and 60° entrance angle.

11. Regularly clean and check the differential compression equipment for
accuracy.

Note: Insure all gages are accurately calibrated within the gage manufacturer’s
calibration specifications.

Revised June 2009 Page 3, Section 72-30

Section 72-30-02 IO-390-A1A6 Maintenance and Overhaul Manual

2. Check equipment for accuracy with the shutoff valve closed and regulated
pressure at 80 psi. The cylinder pressure gage must indicate 80 psi ± 2 psi
while maintaining the regulated pressure at 80 psi for at least 5 seconds.

72-30-02a2 Recommendations For Performing the Differential Compression Check

Note: The following recommendations outline the principles involved and are
intended to supplement the equipment manufacturer’s instructions. Read
and follow the equipment manufacturer’s instructions for the correct
operation of specific testing equipment.

Warning
Take all necessary precautions against accidental firing or rotation of the
engine.

1. Run the engine to normal cylinder head and oil temperatures immediately
preceding the compression check.

2. Ensure the magneto switches are operating correctly before shutdown

following the airframe manufacturer’s operating instructions.

3. Shut down the engine by closing the throttle and placing the mixture control
in “Idle Cut-Off”. Be sure the magnetos are properly grounded.

4. Perform the compression test as soon as possible after engine shutdown to

provide uniform lubrication of the cylinder walls and rings.

5. Verify that the magneto switches and fuel supply switches are all in the
“OFF” position.

6. Verify the security of “P” lead connections.

7. Ensure that the throttle is in the closed position and that the mixture control
is in the “IDLE-CUT-OFF” position.

8. Set aircraft brakes and chock wheels.

9. Disconnect all spark plug leads.

Caution

Leads and spark plugs are very hot. Take precautions to avoid burns.

10. Remove the most accessible spark plug from each cylinder.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-30-02

11. Verify that the air valve on the test equipment is in the closed position.

12. Connect the compression tester to a clean source of compressed air at

approximately 100 to 120 psi.

13. Adjust the regulator of the compression tester to obtain 80 psi on the
regulated pressure gage. The cylinder pressure gage must also read 80 psi ± 2
psi for at least 5 seconds.

Warning
Severe bodily injury or death may result if struck by a rotating propeller.
Always remain clear of the propeller’s blade arc. Ensure the security of
the propeller blade before applying compressed air to the combustion
chamber. Use heavy gloves or rags to protect the hands while holding the
propeller blade. Before attaching the compression tester, check the air
supply regulator to be sure that air pressure to the engine cylinder is not
in excess of 80 psi air pressure or the cylinder can cause the propeller to
turn.

14. Rotate the propeller in the direction of rotation until the piston is coming up
on its compression stroke.

15. Install an adapter in the spark plug bushing.

16. Verify that the compression tester’s air valve is in the “OFF” position and
connect the compression tester’s quick disconnect adapter to the spark plug
cylinder adapter.

17. Secure the propeller and slowly open the air valve and pressurize the cylinder
with 15 to 20 psi. To assure that the piston rings are seated, one person
should move the propeller back and forth slightly with a rocking motion
while air pressure is introduced.

18. Rotate the propeller against this pressure until the piston reaches Top Dead
Center (TDC). A sudden decrease in the force required to move the propeller
indicates TDC. Rotating the propeller past TDC will tend to rotate the
propeller in the direction of rotation.

Note: Back up at least one-half engine revolution and start over if the piston is
rotated past TDC. This backing up is necessary to eliminate the effect of
backlash in the valve operating mechanism and to keep piston rings
seated on the lower ring lands.

19. Secure the propeller blade and continue to open the air valve completely.

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Section 72-30-02 IO-390-A1A6 Maintenance and Overhaul Manual

Warning
The combustion chamber will contain sufficient air pressure to forcefully
rotate the propeller if it is not exactly on TDC. Always remain clear of
the propellers blade arc. Severe bodily injury or death may result if
struck by a rotating propeller.

20. Check the regulated pressure and adjust to 80 psi as necessary.

21. Observe the pressure indicated on the cylinder pressure gage. The difference
between this pressure and the pressure indicated on the regulator pressure
gage is the amount of leakage through the cylinder. The maximum allowable
leakage is 25% of the 80 psi regulated pressure or a reading of 60/80.

(a) A pressure reading of 70 psi or greater is satisfactory.

(b) A pressure reading of 65 psi to 69 psi indicates possible wear and

subsequent compression checks should be made at 100-hour intervals to
monitor wear rate.

Note: Make log book entry to insure that compression check is made at the
next 100-hour interval.

(c) If the pressure reading is 60 psi or lower, or if the monitored pressure

decreases at a rapid rate, a defective cylinder is indicated and removal or
overhaul should be considered.

(d) Low pressure in a single cylinder is indicative of air passing by the

piston or by the valve.

(e) Air discharged from the breather or oil filler tube indicates leakage in the
area of the piston and rings.

(f) Air discharged through the intake system indicates leakage at the intake
valve.

(g) Air discharged from the exhaust system indicates leakage at the exhaust
valve.

22. Pressure readings for all cylinders should be nearly equal. A difference of 5
psi is satisfactory. A difference of 6 to 15 psi indicates a need for further
investigation.

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Note: If the pressure difference does not exceed 15 psi, it may not be necessary
to remove the cylinder. A valve can reseat itself and regain acceptable
compression. Unless the psi differential exceed 15 or unless there are
indications of other conditions, recheck the compression within the next
10 hours of operation.

23. If low compression results are obtained on a cylinder, rotate the engine
through several revolutions with the starter or restart and operate the engine
at least 3 minutes. This will allow the rings to seal with oil. Recheck the
compression on the affected cylinder.

24. If low compression still results on a cylinder, listen for airflow at the exhaust
or intake ports. Airflow at either location indicates a poor seal at the valve
face to valve seat. This may be corrected by “staking” the valves.

(a) Rotate the propeller so the piston will not be at TDC to prevent the valve
from striking the top of the piston during the “staking” operation.

Caution
Staking at TDC will result in damage to the piston and /or valve.

(b) Remove the rocker box cover and place a fiber drift on the rocker arm
directly over the valve stem.

(c) Tap the drift several times with a 1 to 2 lb. hammer to dislodge any
foreign material between the valve face and seat.

(d) Rotate the engine several revolutions to reseat the valves in the normal
manner.

(e) Recheck compression.

25. If low compression still results, check spark plug port seals with a soap
solution to determine if the Heli-coil insert requires replacement.

26. Check cylinder head and barrel with a soap solution for cracks. Cylinders
with cracks must be replaced.

27. Inspect the spark plugs removed from cylinders with low compression.

28. Visually inspect for evidence of cylinder malfunction.

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Section 72-30-02 IO-390-A1A6 Maintenance and Overhaul Manual

29. Perform a boroscopic inspection of the combustion chamber and top of the
piston for evidence of damage.

30. If indicated by testing or inspection, repair and/or replace cylinder

components in accordance with the following procedures 72-30-02b through
72-30-02e.

72-30-02b Cylinder Removal

Refer to Section 72-60-05 for cylinder removal, disassembly and installation
procedures.

72-30-02c Cylinder Inspection

Examine the cylinder head thoroughly. Check for the following possible defects:

1. Loose, scored, pitted, or otherwise damaged valve seats. Replace.

2. Loose or damaged studs. Replace with 0.003, 0.005, 0.007, or 0.012 in.
oversize studs.

3. Loose or damaged spark plug Heli-coil inserts. Replace with oversize insert.

4. Loose, cracked, or scored valve guides. Replace.

5. Nicked, scored, or dented mounting pads for intake and exhaust ports or for
rocker box covers. Replace.

6. Cracked cooling fins. If a cooling fin adjacent to the exhaust port flange is
cracked, a 3/16 in. diameter hole may be drilled as a stop, providing:

● The end of the crack is at least ¼ in. from the base of the metal; or

● The cracked area may be removed from the fin, provided the maximum
removal is no more than one-half the total fin width; or

● The maximum removal is in accordance with Figure 72-60-05-6; or

● No burrs or sharp edges are in evidence; or

● The minimum fillet at the root of the removed portion of the fin has a ¼
in. radius, and the minimum corner at the top of the fin adjacent to the
removed portion has a ½ in. radius; or

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● There is no more than one crack per fin and its depth is no closer than ¼
in. from the base of the metal, and a fin stabilizer is used to reduce
vibration and further deepen the crack.

7. Physically damaged, broken, or bent fins. If a cooling fin is damaged,

broken, or bent, the blended area must not exceed 3/8 in. nor be 3/8 in.
deep, or:

a. There may be no more than four blended fins on the push rod side of the
head, or

b. In addition to the above, a fluorescent penetrant inspection of the

cylinder must be made. Pay particular attention to the areas between the
15th and 20th cylinder fins (counting from the top) on the exhaust port
side of the cylinder and the area around the lower spark plug
counterbore.

c. For cylinder barrel inspection, refer to Section 72-60-05e3 and 72-60-

05e4.

72-30-02d Cylinder Replacement

Refer to Section 72-60-05h for cylinder installation procedure.

72-30-02e Exhaust Valve and Guide Condition Inspection

Use of ST-310 Fixture to Determine Valve Guide Wear or Carbon Build Up

Refer to Figure 72-30-02-3 for Fixture Installation. Valve guide wear (bell
mouthing) occurs on the inside diameter of the valve guide in a straight line with
the centerline of the rocker arm. Valve stem movement must be measured by
moving the valve stem along this line. The ST-310 fixture incorporates two
adjustable self-locking screws located at different angles to accomplish this on
two differently designed angle valve cylinder head configurations. Refer to
Figure 72-30-02-3.

1. Remove the rocker box cover and gasket from the cylinder head.

2. Push out the valve rocker shaft and remove the exhaust rocker arm and
rotator cap.

Caution
Physically separate and identify by cylinder each valve train part as it is
removed, so that each part may be in exactly the same location from
which it was removed.

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3. Remove push rods, shroud tubes and hydraulic tappet assemblies.

Disassemble tappet and clean as described in Section 72-60-05c and 72-60-
05d.

4. Wipe the oil from the top surface of the spring retainer by wiping with a
cloth dampened with solvent. This will increase the friction between the
valve spring retainer and pressure plate and should eliminate any slippage
when the valve stem and spring are moved into position for a measurement.

5. Install the gage adapter over the end of the valve stem and tighten it securely.
If the adapter can be rocked on the valve stem by hand, it is not correctly
secured. The valve retainer keys do not need to be removed from this type
valve stem. Refer to Figure 72-30-02-2.

Figure 72-30-02-2. Gage Adapter Assembled on Exhaust Stem

6. Insure the adjustable self-locking set screws on the ST-310 fixture are backed
out (counterclockwise) to avoid interference with the adapter post attached to
the valve stem. See Figure 72-30-02-3.

Figure 72-30-02-3. Compressor Plate Installed on Cylinder

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-30-02

7. Push the assembled valve stem and gage adapter in against the upper spring
retainer as far as it will go. This will move the valve off of the seat and
eliminate any interference when the valve stem is moved.

Note: In the following steps 8 and 9, a screwdriver with a 3/16 inch blade x 4
inch long shank is sufficient to move the valve both ways. Excessive
pressure applied to the screwdriver will cause erratic measurements.

8. Insert the blade of a screwdriver in the area between the exhaust valve spring
and fixture as shown in Figure 72-30-02-4, and using the pressure plate as a
fulcrum, press the blade of the screwdriver against the exhaust valve spring,
forcing it toward the self-locking set screw as far as it will go. Relax the
pressure on the screwdriver. Friction between the fixture and the outer spring
retainer should keep the valve stem from returning to its normal position. If
the valve stem does have a tendency to move, maintain a slight pressure on
the spring with the screwdriver.

Figure 72-30-02-4. View Showing Screwdriver in Position

to Move Exhaust Valve Stem

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Section 72-30-02 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-30-02-5. Feeler Gage in Position Between Set Screw and Adapter Post

9. Using a .010 inch feeler gage between the set screw and gage adapter as
shown in Figure 72-30-02-5, turn the set screw toward the gage until a slight
drag is obtained on the feeler gage. Do not turn the screw far enough to move
the adapter and valve stem.

10. Using the screwdriver, push the valve spring as far away from the set screw
as it will go, and using a combination of feeler gage blades determine the gap
between the tip of the set screw and the gage adapter. Refer to the following
Table for acceptable limits.
Recommended Allowable Stem Movement
Valve Guide Minimum Clearance Maximum Clearance
ID (In.) (In.) (In.)
.4995/.5005 .015 .030
11. The measurement obtained in step 10 includes the .010 inch used in step 9 as
a starting dimension.
EXAMPLE

.019 in. = Total thickness of gage required to measure valve movement.

-.010 in. = Thickness of gage used to establish a starting point.
.009 in. = Actual amount the valve stem has moved: This indicates
insufficient clearance between the valve stem and valve guide which can be
corrected by reaming the valve guide I.D. to remove a buildup of carbon
deposits. Using the same procedure, if the dimension obtained in step 10. had
been .038 inch, the actual amount the valve stem moved would be .028 inch
indicating that wear on the inside diameter of the valve guide is below the
maximum limit and the valve guide is suitable for further service. If valve stem

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movement is in excess of the maximum limit listed in the table, the valve and
guide must be replaced.
12. Rotate the piston to near its top end of travel again and remove the gage
adapter from the valve stem.

13. Remove the fixture from the cylinder by backing out the capscrews
alternately to release pressure on valve springs evenly.

14. Complete the preceding checks on all cylinders, enter the inspection results
and any corrective action accomplished in the engine log book.

15. Using new seals and gaskets, install the hydraulic tappet assemblies, shroud
tubes, push rods valve rotator caps (if required), rocker arms and shafts, and
check dry tappet clearance. If all parts are returned to their original position,
dry tappet clearance will not change. To check dry tappet clearance, push in
on push rod end of valve rocker and check clearance between the end of the
valve rocker and valve stem tip, using a valve clearance gage. Dry or
unleaded clearance limits are given in the Table of Limits Section.

Modification of ST-310 Fixture to Allow Use of a Dial Indicator

The procedure described above utilizes a feeler gage to measure the distance the
exhaust valve stem has moved. Although this method is satisfactory, it has been
found that it is much easier to measure movement of the valve stem if a dial
indicator is used instead of the feeler gage. Refer to Figure 72-30-02-6 for
modification for a P/N ST-310 fixture.

Figure 72-30-02-6. Details for Modifying Tool ST-310 for Use

With a Dial Indicator (Angle Valve Cylinders)

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Section 72-30-02 IO-390-A1A6 Maintenance and Overhaul Manual

Note: The dial indicator shown in Figure 72-30-02-6 is Model C8IQ

manufactured by Federal Products Corp., Providence R.I. If a
comparable dial indicator is available for use, the adjustment screw holes
in the fixtures can be drilled to accommodate the indicator.

16. Install the adapter post and fixture in the same manner as described in steps
1. through 3. above, and push the adapter post and valve stem in against the
valve spring retainer as far as it will go.

17. Insert the blade of a screwdriver in the area between the valve spring and
fixture and push the valve and adapter post away from the dial indicator as
shown in Figure 72-30-02-7.

18. Move the dial indicator toward the adapter post until the indicator is
preloaded approximately .010 inch, and lock it in place with the set screw.

19. Adjust the dial of the indicator to rear “0” (zero) as shown in Figure 72-30-
02-7.

20. Insert the screwdriver between the fixture and valve spring on the opposite
side and push the valve spring toward the dial indicator as shown in Figure
72-30-02-7. Relax the screwdriver and record the reading on the dial
indicator. The measurement must be within the limits .015 in. to .030 in. If
not, perform the required procedure as described in Step 15 of the preceding
section.

Figure 72-30-02-7. Dial Indicator in Position to Check Valve Guide Clearance

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Figure 72-30-02-8. Pushing Valve Stem and Adapter Post Toward

Dial Indicator to Establish Valve Guide Condition

Use of a “GO/NO-GO” Gage to Determine Vale Guide Wear or Carbon Build

Up

21. Remove all spark plugs and exhaust manifold. If compressed air is to be used
to hold valve, one spark plug should not be removed.

22. Remove rocker box cover and gasket from cylinder.

23. Push out rocker shaft to remove exhaust rocker and rotator cap.

Caution

Physically separate and identify by cylinder and valve location, the valve
train components as they are disassembled, so that each part may be
reinstalled in exactly the same location from which it was removed. Pay
particular attention to valve stem keys. These tend to wear in uniform
distinctive patterns, and must be returned to the same position as they
were removed.

24. Position crankshaft just after bottom center on the intake stroke.

25. Insert about 8 feet of 3/8 inch nylon rope through the spark plug hole; then
turn the crankshaft until the piston moves the rope snuggly against the
exhaust valve.

a. An alternate technique for holding the valve in position is with air

pressure using shop air and a compression check fitting.

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Section 72-30-02 IO-390-A1A6 Maintenance and Overhaul Manual

Caution
The piston is held at bottom dead center by firmly holding the propeller
to prevent the engine from turning when air pressure is applied through
the differential compression device to the combustion chamber. Use
gloves or rags to protect the hands while holding the propeller blade.
Also, before attaching the compression tester, check the air supply
regulator to make sure the air pressure to the cylinder is not excessive.
Air pressure in the cylinder can cause the propeller to turn. Keep clear of
the path of the blades.

26. Compress the exhaust valve spring and remove valve keys. (The rope or air
pressure inserted in the combustion chamber in the preceding step provides a
base to support the valve in the event the keys tend to stick.

27. Remove the nylon rope or bleed off the air pressure and insert light through
the upper spark plug hole. Then start pushing the valve from its guide.
Before the valve stem is free from the guide, secure it from falling into the
cylinder with mechanical pickup fingers, working through the spark plug
holes and/or exhaust ports as shown in Figure 72-30-02-9.

Figure 72-30-02-9. View Through Exhaust Port Showing

Mechanical Fingers Holding Valve Stem

Nominal Exhaust Valve

Guide ID GO Gage NO-GO Gage
.5000 in. .4995 in. *
* - This gage to be sized in accordance with Table of Limits for hours on
engine.
28. With the appropriate gage (GO/NO-GO), check the valve guide for either
wear or carbon build up.

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a. The NO-GO gage must not enter. If it does, the valve guide has had too
much wear and must be replaced in accordance with Section 72-60-05g3.

b. The GO gage side must enter totally inside the valve guide; if such is not
the case or if there is a friction point, ream the guide to the dimensions
recommended in the Table of Limits Section.

29. Using a magnetic pencil and flexible mechanical fingers, position tip of valve
in guide and very carefully work the valve back into its guide. Extreme
caution must be exercised during this operation, making sure the valve is
placed within the guide and not cocked, as damage could be done to the
guide or valve.

Caution
Never use the piston to push the valve through the guide.

Caution
During reassembly, valve train components must be replaced in their
original location. All parts must be in proper alignment to assure correct
dry tappet clearance. Misalignment could result in engine damage.

30. Install valve springs and valve spring seats in same position as removed.
Compress valve spring and install keys in their respective position. In some
cases it has been found that when the valve spring is compressed, the valve
slides down the guide, making it impossible to install the keys. If this
condition exists, reinsert the nylon rope (steps 4. and 5.) to hold valve firmly
on its seat while installing valve keys.

31. Remove hydraulic lifter and clean free of all oil, inspect for any malfunction.
Clean ID of cam follower. Reinstall hydraulic lifter.

32. Install push rod, then rotating cap, rocker arm and shaft.

33. Check dry tappet clearance in accordance with the Service Table of Limits.

34. Install rocker box cover and new gasket.

35. Make sure all flashlights, ropes, etc. have been removed from within the
cylinder before proceeding to the next cylinder.

36. Install spark plugs. (Install exhaust manifold after all exhaust valve guides
are cleaned.)

37. Make appropriate logbook entry.

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72-30-03 RINGS
There are no regularly scheduled maintenance procedures that apply to rings.

72-30-04 PISTONS
There are no regularly scheduled maintenance procedures that apply to pistons.

72-30-05 PUSH RODS

There are no regularly scheduled maintenance procedures that apply to push rods.

72-30-06 VALVES AND VALVE SPRINGS

Other than the exhaust valve and guide inspection, there are no regularly
scheduled maintenance procedures that apply to valves and valve springs.

72-30-07 ROLLER TAPPETS

There are no regularly scheduled maintenance procedures that apply to roller
tappets.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-50-01

72-50-00 LUBRICATION SYSTEM MAINTENANCE

72-50-01 GENERAL INFORMATION

72-50-01a Lubricant Recommendations

Lubricating oil which conforms to both MIL-L-6082 or SAE J1966 straight
mineral-type and MIL-L-22851 or SAE J1899 ashless dispersant-type has been
approved for use in this engine. Refer to table 72-50-01A.

Note: First 50 Hours – During the first 50 hours of operation, it is

recommended that this engine be operated using only mineral oil until
the oil consumption has stabilized. Additive LW-16702 may be used. If
ashless dispersant-type oil is used in a new, newly overhauled, or rebuilt
engine, the break-in or the piston rings and cylinder wall may be delayed
and high engine oil consumption may be experienced. Mineral oil must
also be used following the replacement of one or more cylinders.

Table 72-50-01A. Lubricating Oil Recommendations

Average Ambient Air MIL-L-6082 or SAE J1966 MIL-L-22851 or SAE J1899

Temperature °F (°C) Spec. Mineral Grades Spec. Ashless Dispersant
Grades
See Note A See Note B
See Note C
All temperatures --- SAE 15W-50 or SAE 20W-50

Above 80°F (27°C) SAE 60 SAE 60

Above 60°F (16°C) SAE 50 SAE 40 or SAE 50

30°F to 90°F (-1°C to 32°C) SAE 40 SAE 40

0°F to 70°F (-18°C to 21°C) SAE 30 SAE 30, SAE 40,

or SAE 20W-40
Below 10°F (-12°C) SAE 20 SAE 30 or SAE 20W-30
Notes

A. Average Temperatures – The ambient ground air temperatures listed in the chart are meant only as a
guide. A great deal of personal judgment must be used when selecting the seasonal grade of oil to put into
the engine. For example, if an aircraft is to be flown into an area that is much warmer or colder, only the
personal judgment of the operator can be used to determine what grade of oil to use. When oil inlet
temperatures approach the maximum allowable temperature during operation, it is a good indication that a
higher viscosity oil should be considered.

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B. Mineral Grades – Included in this classification are aviation-grade, mineral-lubricating oils. The
SAE straight mineral grades 20, 30, 40, 50, and 60, as shown in this chart, are equivalent to commercial
grades 55, 65, 80, 100, and 120 and to military grades 1040, 1065, 1080, 1100, and 1120, respectively.
This classification also includes a multiviscosity 20W-50 oil.

C. Ashless Dispersant Grades – This classification describes oil which contains additives. One such
additive has a viscosity-stabilizing effect that helps prevent the oil from thinning out at high operating
temperatures and thickening at low operating temperatures. The additives in these oils extend the
operating temperature range, improve cold engine starting, and lubricate the engine more effectively
during the critical warm-up period. They also make it possible to operate the engine through a wider
range of ambient temperatures and climactic conditions without the necessity of changing the oil. Grades
30, 40, 50, and 60 shown on the chart are equivalent to grades 65, 80, 100, and 120, respectively. Do not
presume that use of these oils will allieviate all of the problems encountered in extremely cold
environments (below 10°F or -12°C). At such low temperatures, preheating the engine and oil supply tank
will be required regardless of the type of oil used.

72-50-01b Lubricant Additives

Caution
The terms “detergent,” “additive,” “compounded,” and “ashless
dispersant” refer to a class of aviation engine-lubricating oils to which
certain substances have been added at the refinery to improve them for
aircraft use. These terms do not refer to those minerals commonly known
as “top cylinder lubricant,” “dopes,” or “carbon remover,” which are
sometimes added to fuel or oil. These products may damage the engine
(pistons, rings, etc.) and their presence in an engine will void the
warranty. Do not use automotive lubricants in Lycoming engines because
they may cause engine failure.

Lycoming has approved an oil additive (P/N LW-16702) containing an anti-

scuffing agent to reduce wear. For engines already in service, add one 6 ounce
can at the next oil change.

Oil additive P/N LW-16702 can be purchased through Lycoming Engines and
authorized Lycoming distributors.

Note: Do not use more additive than recommended above. If it is determined

that the FAA approved lubricating oil being used contains, in the proper
amount, an oil additive equivalent to P/N LW-16702, then no further
action is required. See latest revision of SAIB (Special Airworthiness
Information Bulletin) NE-06-31 for approved additized oils, available at
http:/rgl.faa.gov/

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72-50-01c Lubricant Capacities

The capacity of the oil sump is 8 quarts.

72-50-01d Recommended Oil/Filter Change Intervals and Procedures

1. At 25 hours after the first replacement/screen cleaning – oil change, filter

replacement or pressure screen cleaning and oil sump suction screen check
for new, rebuilt or newly overhauled engines and for engines with any newly
installed cylinders.

2. 25-Hour Interval – oil change, pressure screen cleaning, and oil sump suction
screen check for all engines employing a pressure screen system.

3. 50-Hour Interval – oil change and filter replacement and suction screen
check for all engines using full-flow filtration system.

Note: A total of four (4) months maximum between changes, regardless of

hours of operation.

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72-50-02 SUMP

72-50-02a Suction Screen

A 1.50-18 thread oil plug with a 1.00 in. hex head is provided in the rear of the
oil sump for access to the suction screen.

1. Unscrew the hex head plug and remove the suction screen.

2. Examine the screen carefully before any cleaning operations for any
evidence of metal particles, which indicates possible excessive internal wear
of the engine.

3. Inspect the screen for any distortion, deformation or openings in the mesh.

4. Reinstall with a new crush type gasket. Plug requires 135° angle of turn for
copper gasket.

5. Resafety in accordance with Table 70-00-02B.

Caution

When oil suction screen is removed, extreme care must be taken to see
that the sump plug, located in the extreme end of the scavenger oil
chamber, is not dislodged from its location. If this plug is not secure in
its correct location, lubrication failure will occur with severe damage to
the engine.

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72-50-03 OIL PUMP

There are no regularly scheduled maintenance procedures that apply to the oil
pump.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-50-04

72-50-04 OIL PRESSURE RELIEF VALVE

72-50-04a Scheduled Maintenance

There are no regularly scheduled maintenance procedures that apply to the oil
pressure relief valve.

72-50-04b Pressure Adjustment

In the event a pressure adjustment is required, refer to Appendix III, Section 6,
for adjustment spring specifications.

Oil pressure is adjusted by turning the hex nut on the end of the oil pressure relief
valve. Adjust the oil pressure after the engine is thoroughly warm. Normal oil
pressure can be expected to vary from 100 psi during engine starting and warm-
up to 25 psi at idle when the engine is warm. See oil pressure specifications in
Table 05-10-00A.

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72-50-05 OIL SEALS AND GASKETS

If there are indications of leaking around oil seals and gaskets, identify the source
of the leak and repair as required.

Refer to Section 72-00-02e, Operation Ground Check after Maintenance.

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72-50-06 OIL COOLER

There are no regularly scheduled maintenance procedures that apply to the oil
cooler. Inspections must include a check for secure connections and for dirt or
obstructions in the air flow. Refer to the airframe manufacturer’s instruction
manual for additional information.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-50-07

72-50-07 OIL COOLER BYPASS VALVE

There are no regularly scheduled maintenance procedures that apply to the oil
cooler bypass valve.

High oil temperatures may be an indication that the bypass valve requires service
or replacement.

Refer to Section 72-60-04.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-50-08

72-50-08 OIL FILTER

Replace oil and oil filter at intervals specified in Section 05-20-00 or more often
depending on hours of flying time and type of operation.

72-50-08a Oil Filter/Screen Content Inspection

Note: To insure that no external contaminants enter the oil suction screen, use
clean containers for collection oil, and perform inspection on clean
surfaces.

1. Using approved method (e.g., for full-flow, spin-on filters, use Champion
Tool CT-470 or Airwolf Cutter AFC-470) open the filter.

2. Check the condition of the oil from the filter. Inspect for a high concentration
of aluminum in the oil, indicated by a shining, metallic residue.

3. Drain oil; remove the suction screen from the oil sump and check for metal
particles.

Note: If oil is not contaminated, it may be reused until the 25-hour inspection.

4. Remove the paper element from the filter.

5. Carefully unfold the paper element and examine the material trapped in the
filter.

6. When performing the regular filter/screen inspection, check for the presence
of metal particles, shaving or flakes.

Note: In new, rebuilt or newly overhauled engines some small particles of

metallic shavings might be found, but these are generally of no
consequence and should not be confused with particles produced by
impacting, abrasion or pressure.

7. Evidence of metal contamination found in the filter element or screen

requires further examination to determine the cause. Below is a list of
recommended actions based on the appearance and approximate quantity of
particles.

a. One to nine (1/16 inch diameter or less) pieces of metal – place aircraft
back in service and check oil filter or screen at next scheduled oil
change/oil filter replacement.

b. 10 to 20 small (1/16 inch diameter or less) pieces of shiny flake-like,

nonmagnetic, or 10 or fewer short hair-like pieces of magnetic material –

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Section 72-50-08 IO-390-A1A6 Maintenance and Overhaul Manual

place engine back in service and again check oil filter or screen in 25
hours.

c. 20 to 40 small pieces as in step (b) – place the aircraft back in service

and check oil filter or screen at the next 10 hours.

d. As in step (b), but larger amount, such as 45-60 small pieces – change
filter or clean screen, drain oil, and refill. Run engine on ground for 20 –
30 minutes making certain not to exceed any temperature limits. Inspect
filter/screen. If clean, fly aircraft for 1 to 2 hours and again inspect
filter/screen. If clean, inspect filter/screen after 10 hours of flight time.

Note: In items (e) through (j) below, the engine must be removed from service
until the source of the metal is determined and corrective maintenance
has been accomplished.

e. Pieces of metal ranging in size of broken lead pencil point or greater.

Remove suction (sump) screen to check for pieces of metal that may
have fallen into the sump. In any event, ground aircraft and conduct
investigation. A mixture of magnetic and nonmagnetic material in this
case often times means valve or ring and piston failure. Removing
bottom spark plugs usually reveals the offending cylinder.

f. Nonmagnetic plating averaging approximately 1/16 inch in diameter;

may have copperish tint. Quantity found – ¼ teaspoonful or more;
ground aircraft and investigate.

g. Same as in step (b) but may be slightly larger in size and minus
copperish tint. On direct drive engine, propeller action may be impaired.
Ground aircraft and investigate.

h. Nonmagnetic metal brass or copperish colored. Resembles coarse sand in

consistency. Quantity of ¼ teaspoonful or more – ground aircraft and
investigate.

i. Anytime metal is found in the amount of ½ teaspoonful or more, it is

justification for engine removal.

j. If any single or several pieces of magnetic or nonmagnetic metal larger

than previously mentioned are found, ground aircraft.

Note: If the origin of the metal contamination cannot be determined, a call may
be made to the Lycoming Product Support Department. A good
description of the metal may result in placing its origin. When phoning
Lycoming or when returning metal removed from engines, supply the
complete engine model designation, serial number, history of engine, oil

Page 18, Section 72-50 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-50-08

temperatures, oil pressures, and any unusual behavior of the engine on

the ground or during flight. Do not ship material to Lycoming without
first calling the Product Support Department.

8. If examination of the oil filter or screen, per the above, indicates abnormal
aluminum or iron content contact a technical representative of Lycoming
Product Support Department.

9. After examination, replace oil. Start engine and check for leakage.

72-50-08b Spectrographic Oil Analysis

Note: Spectrographic oil analysis does not replace recommended maintenance
practices such as oil filter, pressure screen, and suction screen content
inspection, cylinder differential pressure compression check, and
boroscopic examination, however, Lycoming does encourage the use of
spectrographic oil analysis at every oil change as method of monitoring
engine component wear rate.

1. Collect an oil sample and submit it for analysis by a qualified facility. The
facility used for the spectrographic oil analysis should be a facility that
specializes in aircraft engines. It is recommended that the same facility be
used for each oil analysis due to the differences in laboratory testing
standards. Use care to insure that the oil sample is free of outside
contaminants.

Note: Typically, the first oil analysis of a new, rebuilt, or newly overhauled
engine will indicate higher concentrations of metal. After an initial
break-in period, metal content should decrease rapidly to a level that
remains essentially constant. Remember, oil analysis is a trend
monitoring, so no conclusions should be made until a trend is
established.

2. If an oil analysis report indicates elevated level of aluminum (above 30 parts

per million for non-turbocharged engines) or iron (above 100 parts per
million for non-turbocharged engines), contact a technical representative at
the Lycoming Factory Product Support Department.

3. If in a continuing program of oil analysis results show a trend toward an

increase in aluminum or iron content, inspect contents of the filter and screen
in accordance with the procedures in 72-50-08a.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-50-09

72-50-09 OIL TEMPERATURE SENSING SYSTEM

The oil temperature probe location is on the top of the oil filter adapter.

The oil temperature probe and oil temperature gages are components that are
furnished by the airframe manufacturer. Consult the airframe manufacturer’s
instruction manual for installation.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-01

72-60-00 OVERHAUL SECTION

72-60-01 INTRODUCTION
This overhaul section contains the necessary information, arranged in a logical
sequence, for performing a complete overhaul on the Lycoming IO-390-A Series
engine. Separate descriptions of each engines component are presented in
sections 72-60-03 through 72-60-09.

Since there are various overhaul practices and instructions applicable to each
component subsystem, these general instructions are grouped in section 72-60-02
to avoid repetition. Those responsible for performing overhaul procedures must
read and thoroughly understand this information before beginning any overhaul
procedure. It is essential to follow these instructions to ensure safe operation and
to contribute to the long life, economy, and satisfactory operation of this engine.

In this section, all references to locations of various components will be

designated as if viewing the engine from the rear (anti-propeller). The front of the
engine is considered to be the propeller end, and the oil sump to be on the bottom
of the engine. Cylinders are numbered from front to rear with the odd-numbered
cylinders on the right-hand side, and rotation of the crankshaft when viewed from
the rear is clockwise. All references to direction of rotation of the various
accessory drives are as viewed facing the accessory drive mounting pad.

Note: Information concerning removal and replacement of accessories is

provided in this section to facilitate overhaul of the IO-390-A Series
engine.

Revised June 2009 Page 1, Section 72-60

Section 72-60-01 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-01a Disassembly Check List Procedure

Reference
Procedure Section

• Disconnect leads and wiring................................................................72-60-03

• Remove accessories.............................................................................72-60-04

• Remove accessory housing and accessory drive gears........................72-60-04

• Remove drainback tubes ...................................................................72-60-05b

• Remove intake pipes .......................................................................72-60-07b1

• Remove fuel injector .......................................................................72-60-07b2

• Remove fuel lines and clamps.........................................................72-60-08b1

• Remove induction housing..............................................................72-60-07b3

• Remove oil sump.............................................................................72-60-07b4

• Remove oil sump baffle ....................................................................72-60-06a

• Remove intercylinder baffles ............................................................72-60-05a

• Remove spark plugs ............................................................................74-20-03

• Remove rocker box covers ................................................................72-60-05b

• Remove rocker shaft cover plates .....................................................72-60-05b

• Remove rocker shafts, rockers, push rods, shroud tubes and

valve rotator caps. Keep parts separate for reassembling in
the correct location ............................................................................72-60-05b

• Remove cylinders and pistons...........................................................72-60-05b

• Remove connecting rods one at a time. Insure connecting

rods are supported .............................................................................72-60-05b

• Split crankcase...................................................................................72-60-06b

• Remove crankshaft, camshaft, bearings ............................................72-60-05b

• Remove roller tappet bodies............................................................72-60-05b1

Page 2, Section 72-60 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-02

72-60-02 STANDARD PRACTICE FOR OVERHAUL

A visual inspection of each component or part must be made at the time of or
immediately following its removal from the engine. Lay out all parts in an
orderly manner as they are removed from the engine. Do not perform the
cleaning operation until this initial visual inspection has been completed.

All loose studs, cracked cooling fins, loose or damaged fittings, or other damage
discovered during disassembly or the initial visual inspection should be carefully
tagged and noted to prevent their being overlooked during regular inspection.

72-60-02a Tools Required for Overhaul

In addition to a standard set of mechanic’s tools, the tools listed in
Table 72-60-02A are suggested for overhaul.

Table 72-60-02A. Tools Required for Overhaul

Tool No. Nomenclature and Description

64514 Gage, 0.4040 to 0.4050 in. intake valve

64526-2 Cylinder Holding Block

64530 Gage, Connecting Rod Parallelism and Squareness

64535 Drift, Connecting Rod Bushing Removal

64536 Drift, Connecting Rod Bushing Replacement

64537 Gage, Flat Plug – Connecting Rod Bushing Retention

64540 Fixture, Rebushing Valve Rocker

64541 Burnisher, Valve Rocker Bushing

64542 Gage, Plug, Valve Rocker Bushing ID (Finish)

64545 Block, Vee – Check Crankshaft Run (2 required)

64553 Basket, Valve Parts, Cleaning

64580 Burnisher, Connecting Rod Bushing

64593 Expanding and Staking Tool, 18 mm Spark Plug Heli-coil Insert

64594 Inserting Tool, 18 mm Spark Plug Heli-coil Insert

64595 Removing Tool, 18 mm Spark Plug Heli-coil Insert

64596-1 Tap, 18 mm Heli-coil Spark Plug Bottoming Tap 0.010 in. OS

August 2008 Page 3, Section 72-60

Section 72-60-02 IO-390-A1A6 Maintenance and Overhaul Manual

Tool No. Nomenclature and Description

64597 Fixture, Remove, Replace, Burnish Connecting Rod Bushing

64613 Gage, Rocker Shaft Bushing Rejection

64644 Fixture, Valve Guide Replacement

64681 Driver, Crankshaft Welch Plug

64697 Pointer, Ignition Timing

64713 Expander, Piston Ring

64767 Gage, Connecting Rod Bushing ID Finish

64782 Puller, Slide Hammer – Medium

64810 Gage, Plug, Rocker Shaft Bushing Hole in Cylinder Head

64811 Gage, Plug, 0.005 in. OS, Rocker Shaft Bushing Hole in Cylinder
Head (See ST-191 for 0.010 in. OS)

64812 Reamer, 0.005 in. OS – Outer Rocker Shaft Bushing Hole in

Cylinder Head

64813 Reamer, 0.010 in. OS – Outer Rocker Shaft Bushing Hole in

Cylinder Head

64814 Drift, Rocker Shaft Bushing Removal

64815 Drift, Outer Rocker Shaft Bushing Installation

64816 Drift, Inner Rocker Shaft Bushing Installation

64819 Reamer, Semi-Finish, Outer Rocker Shaft Bushing ID

64820 Reamer, Semi-Finish, Inner Rocker Shaft Bushing ID

64821 Reamer, Finish Outer Rocker Shaft Bushing ID

64822 Reamer, Finish Inner Rocker Shaft Bushing ID

64823 Gage, Plug-Rocker Shaft Bushing ID

64838 Reamer, 0.005 in. OS Inner Rocker Shaft Hole in Cylinder Head
(Used with 64812 reamer for angle head cylinder.)

64839 Reamer, 0.010 in. OS Inner Rocker Shaft Hole in Cylinder Head
(Used with 64813 reamer for angle head cylinder.)

64843 Puller, Piston Pin

64862 Spotfacer, Inner Rocker Shaft Bushing

64872 Puller, Remove and Install Crankshaft Counterweight Bushings

Page 4, Section 72-60 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-02

Tool No. Nomenclature and Description

64874 Reamer, 0.005 in.OS counterweight Bushing Holes (See ST-210
for 0.0075 in. OS)

64875 Reamer, 0.010 in. OS Counterweight Bushing Holes (See ST-211

for 0.0125 in. OS)

64876 Reamer, 0.015 in. OS Counterweight Bushing Holes

64878 Fixture, Grind Bushings in Dynamic Counterweight

64885 Intercylinder Baffle Tool

64892 Gages, Check Circlips in Counterweights

64899 Adapter, Magnetic Particle Inspection of Hydraulic Tappets (Use

with ST-387)

64923 Gage, Valve guides with 0.4985 to 0.4995 in., 0.4995 to 0.5005 in.
ID

64924-1 Reamer, 0.010 in. oversize

64924-2 Reamer, 0.020 in. oversize

64924-3 Reamer, 0.030 in. oversize

64924-4 Reamer, 0.040 in. oversize

64928 Gage, 0.005 in. oversize

64929 Gage, 0.010 in. oversize

64930 Gage, 0.020 in. oversize

64931 Gage, 0.030 in. overisze

64940 Gage, Standard

64941 Tool, Remove Hydraulic Tappet Assemblies

64942 Wrench (1/2 in. Allen) Cylinder Base Nut

64943 Wrench (3/8 in. Allen) Cylinder Base Nut

64945 Gage, Connecting Rod Bolt Stretch

ST-23 Gage, Valve Clearance 0.028 – 0.080 in.

ST-25 Compressor, Valve Spring

ST-54-1 Cutter, Valve Seat (Exhaust) (0.010 in. OS)

ST-54-2 Cutter, Valve Seat (Exhaust) (0.020 in. OS)

ST-54-3 Cutter, Valve Seat (Exhaust) (0.030 in. OS)

August 2008 Page 5, Section 72-60

Section 72-60-02 IO-390-A1A6 Maintenance and Overhaul Manual

Tool No. Nomenclature and Description

ST-55-1 Cutter, Valve Seat (Intake) (0.010 in. OS)

ST-55-2 Cutter, Valve Seat (Intake) (0.020 in. OS)

ST-55-3 Cutter, Valve Seat (Intake) (0.030 in. OS)

ST-62 Driver, Special Length for use with Valve Seat Cutters

ST-63 Adapter, Hand Drive for use with ST-62 Driver

ST-64 Drift, Valve Seat Replacement (1.870 to 2.040 in.)

ST-65 Drift, Valve Seat Replacement (1.575 to 1.710 in.)

ST-66 Pilot, Valve Seat Cutter (Standard)

ST-66-1 Pilot, Valve Seat Cutter (0.010 in. OS)

ST-66-2 Pilot, Valve Seat Cutter (0.020 in. OS)

ST-66-3 Pilot, Valve Seat Cutter (0.030 in. OS)

ST-66-4 Pilot, Valve Seat Cutter (0.040 in. OS)

ST-66-5 Pilot, Valve Seat Cutter (0.005 in. OS)

ST-67 Pilot, Valve Seat Cutter (Standard)

ST-67-1 Pilot, Valve Seat Cutter (0.010 in. OS)

ST-67-2 Pilot, Valve Seat Cutter (0.020 in. OS)
ST-67-3 Pilot, Valve Seat Cutter (0.030 in. OS)
ST-67-4 Pilot, Valve Seat Cutter (0.040 in. OS)
ST-67-5 Pilot, Valve Seat Cutter (0.005 in. OS)
ST-73 Gage, Counterweight Dial Bore (0.7485/0.7505 in. ID of
Bushings) Replace Bushings in Counterweights
ST-91 Gage, Counterweight Squareness (Check Parallel and Squareness
of Finished Inside Diameter of Bushing Hole)
ST-92 Driver, Counterweight Bushing (Remove and Install Bushings)
ST-93 Fixture Assembly, Counterweight (Install Bushings in
Counterweights)
ST-93-3 Spacer, Control Depth of Bushing – 0.370 in. thick (detail of ST-
93)
ST-93-5 Spacer, Control Depth of Bushing – 0.440 in. thick (detail of ST-
93)

ST-94 Gage, Counterweight Bushing Location (Check Hole Location

After Grinding)

Page 6, Section 72-60 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-02

Tool No. Nomenclature and Description

ST-95 Weight, Counterweight Balancing (0.004 pound to check Balance
of Counterweight after Rebushing)

ST-96 Arbor, Counterweight Balancing (Check Balance of

Counterweights after Rebushing)

ST-115 Tool, Install and Remove Propeller Flange Bushings

ST-143-1 Reamer, Valve Guide ID Exhaust (Ni-Resist) – Pilot Dia.

0.4828/0.4833 in. – Finished ID 0.4995/0.5005 in. for large ID
valve guide replacement (See ST-155 for Plug Gage.)

ST-143-2 Reamer, 0.4785 to 0.4800 in.

ST-155 Gage, Plug, Valve Guide ID (Exhaust) – All cylinder heads with
0.4995/0.5005 in. ID valve guide hole

ST-160 Pilot Bar, Assembling Rocker Arms to Cylinder Head

ST-184 Kit, Heli-coil Repair

ST-191 Gage, Plug, 0.010 in. OS, Rocker shaft bushing hole in cylinder
head (See 64811 for 0.005 in. OS.)

ST-212 Gage Blocks, Crankshaft Counterweight Bushing to check

parallelism of counterweight bushing to crankshaft

ST-222 Plate, Torque Hold-Down

ST-222-2 Insert, Torque Hold-Down Plate (Detail of ST-222)

ST-232 Fixture, Valve Seat Replacement and Refacing

ST-236 Arbor, Connecting Rod Slave Bolts

ST-251 Socket, Connecting Rod Nut

ST-270 Plate, Bushing (Crankcase) – Drill and ream crankcase for

standard thru-stud dowels

ST-271 Puller, Crankcase Thru-Stud

ST-280 Fixture, Ream Crankshaft Counterweight

ST-288 Socket, Spark Plug Wrench 7/8 in. Hex

ST-295 Drift, Crankshaft, Oil Plug size 1.251/1.254 in.

ST-310 Gage, Check Bell-Mouthing of Exhaust Valve Guides

ST-317 Driver, Crankcase Thru-Stud

ST-338 Reamer, (Short) Hand-Expansion Valve Guide ID

August 2008 Page 7, Section 72-60

Section 72-60-02 IO-390-A1A6 Maintenance and Overhaul Manual

Tool No. Nomenclature and Description

ST-340 Former, Oil Relief Valve Seat (Use with ST-245)

ST-345 Wrench, “T” Bar – Spark Plug (Use with ST-288)

ST-383 Tool, Crankshaft Oil Seal Installation

ST-387 Fixture, Tappet Body Magnaflux

ST-388 Reamer, Guide and Stop – Oil temperature By-Pass Valve Seat

ST-389 Tool, Crankcase separating

ST-429 Gage, Plug Valve Guide OD (Intake and Exhaust) (STD)

ST-429-1 Gage, Plug Valve Guide OD (Intake and Exhaust) (0.010 in. OS)

ST-429-2 Gage, Plug Valve Guide OD (Intake and Exhaust) (0.020 in. OS)

ST-429-3 Gage, Plug Valve Guide OD (Intake and Exhaust) (0.030 in. OS)

ST-429-4 Gage, Plug Valve Guide OD (Intake and Exhaust) (0.040 in. OS)

ST-429-5 Gage, Plug Valve Guide OD (Intake and Exhaust) (0.005 in. OS)

ST-430-1 Reamer, Valve Guide OD (Intake and Exhaust) (0.010 in. OS)

ST-430-2 Reamer, Valve Guide OD (Intake and Exhaust) (0.020 in. OS)

ST-430-3 Reamer, Valve Guide OD (Intake and Exhaust) (0.030 in. OS)

ST-430-4 Reamer, Valve Guide OD (Intake and Exhaust) (0.040 in. OS)

ST-430-5 Reamer, Valve Guide OD (Intake and Exhaust) (0.005 in. OS)

ST-431 Gage, Plug Valve Guide OD (Exhaust) (STD)

ST-431-1 Gage, Plug Valve Guide OD (Exhaust) (0.010 in. OS)

ST-431-2 Gage, Plug Valve Guide OD (Exhaust) (0.020 in. OS)

ST-431-3 Gage, Plug Valve Guide OD (Exhaust) (0.030 in. OS)

ST-431-4 Gage, Plug Valve Guide OD (Exhaust) (0.040 in. OS

ST-431-5 Gage, Plug Valve Guide OD (Exhaust) (0.005 in. OS)

ST-431-1 Reamer, Valve Guide OD (Exhaust) (0.010 in. OS)

ST-432-2 Reamer, Valve Guide OD (Exhaust) (0.020 in. OS)

ST-432-3 Reamer, Valve Guide OD (Exhaust) (0.030 in. OS)

ST-432-4 Reamer, Valve Guide OD (Exhaust) (0.040 in. OS)

ST-432-5 Reamer, Valve Guide OD (Exhaust) (0.005 in. OS)

Page 8, Section 72-60 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-02

Tool No. Nomenclature and Description

ST-443 Seal Puller and Installation Tool to Remove and Install STD-2217
Seal in Vacuum Pump Adapter
ST-485 Compressor, Piston Ring
Available
from Tool Spring Tester (Imada DPS-220R or equivalent)
Vendor

72-60-02b Cleaning
Prior to disassembly, clean engine. For general cleaning guidelines refer to
Section 70-00-04.

Note: Stains and residues are possible indications of leaks or damage. Prior to
cleaning, determine the source.

All engine parts must be thoroughly cleaned to facilitate further inspections. Two
methods used to clean engine parts are degreasing and decarbonizing.

To degrease the components, immerse them in (or spray them with) a suitable
hydrocarbon-based solvent to remove grease or oil residues, dirt, and soft carbon.

Caution

For handling, storage, use, and disposal of materials, comply with all
federal, state, and local regulations.

Caution
Use of other than hydrocarbon-based solvents can be harmful to
aluminum and magnesium. Any water-based degreasing solutions
containing caustic compounds or soap are potentially dangerous to
aluminum and magnesium. The pores of the metal may become
impregnated by such compounds and cause oil foaming when the engine
is returned to service. Whenever it is necessary, to use water-based
solutions, it is imperative that the parts be completely and thoroughly
rinsed in clean, boiling water after degreasing.

If hard carbon remains on the interior surfaces of some components after

degreasing, soak them in a tank containing a heated decarbonizing solution to
loosen these deposits. A variety of commercial decarbonizing agents are
available, including Gunk, Penetrol, Carbrax, Super Chemaco, and Gerlach No.
70. Decarbonizers, like degreasing agents, fall into two categories: petroleum or
hydrocarbon-based and water-based. The above caution concerning use of water-
based degreasers applies to decarbonizers as well.

August 2008 Page 9, Section 72-60

Section 72-60-02 IO-390-A1A6 Maintenance and Overhaul Manual

Caution

Regardless of the method and type of degreasing agent used, coat and
spray all parts with lubricating oil immediately after cleaning to prevent
corrosion.

Caution

Avoid the use of heated decarbonizing solutions on magnesium castings

unless the operator is thoroughly familiar with the particular solution
being used.

Caution

Do not immerse steel and magnesium parts in the same decarbonizing

tank because this practice often results in corrosion damage to the
magnesium parts.

Decarbonizing will usually loosen most of the hard carbon deposits remaining
after degreasing. If any deposits remain after decarbonizing, remove them by
brushing, scraping, or grit-blasting.

When grit-blasting parts, do not use sand or any metallic abrasive. It is

recommended that only mildly abrasive organic mediums such as rice, baked
wheat, or crushed walnut shells be used. Plastic pellets may also be used. All
machined surfaces must be adequately masked and all openings tightly plugged.
When grit-blasting housings, plug all drilled oil passages with rubber plugs or
other suitable material to prevent foreign matter from entering the housing. Valve
seats are the one exception; these may be left unprotected during grit-blasting the
cylinder head combustion chamber. In this instance, grit-blasting cuts the glaze
that tends to form on the valve seats and facilitates valve seat reconditioning.

Caution
Under no circumstances must the piston ring grooves be subjected to
grit-blasting. If necessary, soak the piston in petroleum solvent and
scrape with a wooden scraper to remove deposits.

Decarbonizing solutions will generally remove most of the enamel from exterior
surfaces. Remove all remaining enamel by grit-blasting, particularly in the
crevices between cylinder cooling fins.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-02

Once all the parts have been cleaned, rinse them in a petroleum-based solvent.
Remove any loose particles and dry them by blasting with clean compressed air.
Apply a liberal coating of lubricating oil to all surfaces immediately after
cleaning to prevent corrosion.

72-60-02c Inspection

72-60-02c1 General
The inspection of engine parts during overhaul is divided into three categories:
visual, structural, and dimensional. The first two deal with the structural defects
in parts, the third deals with the size, shape, and fit.

Visual inspection should precede all other inspection procedures. Do not clean
any parts prior to visual inspection, since indications of dangerous operating
conditions can often be detected from the residual deposits found in some
particular recess of the engine.

Structural failures can be determined by several different methods depending on

the part involved. The following are a few of the methods employed: magnetic
particle, dye penetrant, penetrant, x-ray, and various electronic methods.

Perform dimensional inspections in accordance with the measurements and

tolerances included in the Table of Limits.

It is recommended that an inspection and overhaul form that contains a list of all
engine components be used when disassembling an engine. Prepare this form so
that all inspection and overhaul procedures can be checked off and remarks
noted. This will ensure that no part is inadvertently overlooked.

72-60-02c2 Bearing Surfaces

Examine all bearing surfaces for scoring, galling, and wear. Considerable
scratching and light scoring of aluminum bearing surfaces in the engine will do
no harm and should not be considered cause for rejection of the part, provided it
falls within the clearances set forth in the Table of Limits. Even though the part
may come within specified limits, it should not, however, be reassembled into the
engine unless inspection shows it to be free of other serious defects. Examine ball
bearings visually and by feel for roughness, flat spots, flaking or pitting of races,
and for scoring on the outside of the races. Check all journal surfaces for galling,
scores, misalignment, and out-of-round condition. Check shafts, pins, etc., for
straightness. This may be done in most cases by using vee blocks and a dial
indicator.

August 2008 Page 11, Section 72-60

Section 72-60-02 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-02c3 Gears
Examine all gears for evidence of pitting and excessive wear. These conditions
are of particular importance when they occur on the involute of the teeth; deep pit
marks in this area are sufficient cause to reject the gear. Bearing surfaces of all
gears should be free from deep scratches. However, minor abrasions may be
dressed out with a fine abrasive cloth.

72-60-02c4 Corrosion on Stressed Areas

Pitted surfaces in highly stressed areas resulting from corrosion can cause
ultimate failure of the part. Carefully examine all parts for evidence of such
corrosion. The part must be rejected if pitting exists on any of the surfaces to the
extent that it cannot be removed by polishing with a crocus cloth or other mild
abrasive.

72-60-02c5 Screwed Fittings

Inspect screwed fittings (any parts such as threaded fastenings or plugs) for the
condition of threads. Badly worn or mutilated threads are unacceptable; the parts
must be rejected. However, small defects such as slight nicks or burrs may be
dressed out with a small file, fine abrasive cloth, or stone. The part must be
replaced with a new one if it appears to be distorted, badly galled, or mutilated by
overtightening or using improper tools.

72-60-02c6 Magnetic Inspection

The possibility of structural failures in engine parts makes careful inspection an
essential operation for the reuse of all parts. Structural defects in ferro-magnetic
steel parts can be detected by magnetic particle inspection.

Magnetic particle inspection is an acceptable method of inspecting the following

ferro-magnetic parts:

● Crankshaft

● Camshaft

● Cylinder Barrels

● Connecting Rods

● Counterweights

● Crankcase Thru Studs

● Rocker Arms

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-02

● Rocker Shafts

● Push Rods

● Piston Pins

● Valve Springs

● Valves

● Steel Gears and Shafts

● Tappet Bodies

● Brackets

● Lifting Straps

Special attention must be given to the proper cleaning of parts to ensure complete
removal of all traces of oil, grease, and dirt prior to magnetic particle inspection.
This can be accomplished best in a vapor degreaser using trichlorethylene as a
solvent or an equivalent environmentally friendly cleaning method. A 3 to 7
power magnifying glass must be used to aid in inspection of the parts. Once parts
are deemed acceptable, they must be demagnetized and then cleaned before being
reused.

Caution
Prior to reinstallation be sure parts have been demagnetized.

PERSONNEL QUALIFICATIONS:

Personnel performing Magnetic Particle Inspection must be qualified and

certified in accordance with ASNT Personnel Qualification SNT-TC-1A or NAS-
410.

INSPECTION TECHNIQUE:

A technique must be used that is capable of detecting the smallest indication

regardless of its orientation to the magnetic flux. This technique must establish at
least two magnetic fields, perpendicular to one another, in a plane parallel to the
surface being inspected.

The Magnetic Particle Inspection must be performed in accordance with a written

procedure which describes the technique, how to perform the inspection based on
the technique, and the equipment being used.

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Section 72-60-02 IO-390-A1A6 Maintenance and Overhaul Manual

A person who is qualified and certified to Level III in accordance with ASNT
Personnel Qualification SNT-TC-1A or NAS-410 must approve the Written
Procedure and Inspection Technique. ASTM E 1444 Standard Practice for
Magnetic Particle Inspection Examination must be used as a guideline for
establishing Magnetic Particle Inspection requirements.

Some odd shaped parts may require alternate methods of non-destructive testing
such as fluorescent dye penetrant inspection. When penetrant inspection is
needed, ASTM E 1417 must be used for penetrant inspection processing control.

72-60-02d Repair and Replacement

72-60-02d1 Damaged Parts

Remove abnormal damage such as burrs, nicks, scratches, scoring, or galling
with a fine oil stone, crocus cloth, or any similar abrasive substance. Following
any repairs of this type, carefully clean the part to be certain that all abrasive has
been removed and then check the mating part to ensure that the clearances are not
excessive. Flanged surfaces that are bent, warped, or nicked may be repaired by
lapping to a true surface on a surface plate. Again, the part should be cleaned to
ensure that all abrasive has been removed. Defective threads can sometimes be
repaired with a suitable die or tap. Small nicks can be removed satisfactorily with
Swiss pattern files or small, edged stones. Pipe-tapped threads should not be
tapped deeper to clean them, because this invariably results in an oversized
tapped hole. If scratches or galling are removed from a bearing surface of a
journal, it should be buffed to a high finish. Generally, it is impossible to repair
cracks.

72-60-02d2 Painted Parts

Parts requiring paint for protection or appearance should be painted in
accordance with the following list of approved materials: thinner – toluene or
equivalent (AMS-3180 or equivalent Federal Spec. TT-T-548); primer – zinc
chromate (AMS-3110 or equivalent MIL-P-8585); enamel – phthalate resin type
(AMS-3125F or equivalent MIL-E-7729).

Note: Mask all machined bosses before painting. Do not paint areas under
hold-down nuts where torque is required.

72-60-02d3 Aluminum and Steel Parts

Parts should be cleaned and degreased prior to painting. Apply one coat zinc
chromate primer, thinned with approximately two parts toluene, and air dry.
Apply one coat of enamel and bake at 250°F (121°C), to 300°F (148°C), ½ hour.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-02

Enamel may be allowed to air dry but an inferior finish will result. Parts from
which paint has not been removed may be repainted without the primer coat.

72-60-02d4 Magnesium Parts

Thoroughly clean magnesium parts with a dichromate treatment prior to painting.
This treatment consists of cleaning all traces of oil and grease from the part using
a neutral, non-corrosive degreasing medium followed by a rinse, after which the
part is immersed for 45 minutes in a hot dicromate solution (3/4 lb. of sodium
dichromate to 1 gallon of water at 180°F (82°C) to 200°F (94°C), quantity as
required). Wash the part thoroughly in cold running water, dip in hot water, and
dry in an air blast. Immediately thereafter, paint the part with a prime coat and
engine enamel in the same manner as prescribed for aluminum parts.

72-60-02d5 Shroud Tubes

Thoroughly clean the shroud tubes. After the shroud tubes dry, paint the outside
with engine enamel.

All paint applied in these operations should be sprayed; however, when necessary
to use a brush, take care to avoid an accumulation of paint pockets.

72-60-02d6 Replacement of Studs

Replace any studs that are bent, broken, damaged, loose or rusted/corroded that
cannot be cleaned. The method of removing studs depends on the type of stud
and the manner in which it is broken. The procedure for removing and replacing
studs is as follows.

1. If sufficient thread area is available on stud, use a collet grip tool consisting
of a tapered collet that threads onto the stud and a housing that slips over the
collet. Tighten the bolt on the top of the housing and draw the collet into the
housing to lock the puller on the stud with a tight grip.

2. If the collet-type tool cannot be used, drill a small hole into the stud. Use a
pilot bushing to guide the drill into the center of the stud when the stud is
broken beneath the surface of the crankcase. Redrill the hole to enlarge it to
accommodate the proper size extractor. Remove the stud with the extractor.

After removing the studs, check for the size and condition of the threads in the stud holes to
determine whether oversize studs must be used for replacement. Coat the threads of the studs with
thread lubricant, Loctite P/N 1167237 Food Grade Anti-Seize, and drive the stud to the correct depth
using a suitable stud driver. Check minimum drive torque in the Table of Limits.

Revised October 2010 Page 15, Section 72-60

Section 72-60-02 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-02d7 Corrosion Prevention

Coat all steel parts with preservative oil at the conclusion of all repair operations
and subsequent inspection.

72-60-02e General Reassembly Procedures

72-60-02e1 Corrosion Prevention

Prior to assembly of subassemblies, clean all parts to remove all traces of
preservative oil and accumulated foreign matter. During assembly, cover all steel
parts with a heavy coat of preservative oil. Refer to Section 72-00-05. This
mixture should be used on all machined surfaces, especially on bearing surfaces,
cylinder bores, and piston rings. The practice of using plain lubricating oil during
assembly is not recommended.

72-60-02e2 Prelubrication of Parts Prior to Assembly

Many premature failures of parts have been traced directly to improper
prelubrication during engine assembly. If parts are not properly lubricated or if
an inferior lubricant is used, many of the engine parts will become scored before
the engine oil goes through its first cycle and can lubricate the engine. This leads
to premature part failure prior to normal service life and, in some cases, engine
failure before normal service hours have been accumulated. It is of utmost
importance to adhere to the following recommendations at engine assembly.

● Coat the camshaft lobes, face of tappet bodies, and rocker tips with Lubri-
bond (A) or equivalent.

● Coat the valve stems and the interior of the valve guides with Texaco
Molytex “O” or equivalent.

● Coat the piston pin plugs with Lubri-bond (A) or equivalent.

● Coat the connecting rod bearings with engine oil.

● Coat the crankshaft thrust bearing face with Lubri-bond (A) or equivalent.

● Coat all other parts with a mixture of 15% prelubricant (STP or equivalent)
and 85% SAE No. 50 mineral base aviation-grade lubricating oil.

72-60-02e3 Oilite Bushings

During overhaul cleaning operations it is possible to wash the oil from these
bushings. If a bushing has been replaced and either reamed or broached, its
porosity may be affected. Therefore, before the bushings are reassembled into the

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-02

engine, they must be impregnated by immersing them for at least 15 minutes in

engine oil that has been heated to 140°F (60°C).

72-60-02e4 Table of Limits

Consult the Table of Limits (Appendix III) to determine the backlash and end
clearance of gears, the clearance between mating machined parts, the clearance
between moving parts that are close in contact with each other, and the torque
limits for various nuts, screws, and fastenings.

72-60-02e5 Oil Seals and Gaskets

When building up an engine during major overhaul, replace all oil seals and
gaskets throughout the engine. Consult the applicable parts catalog to order
complete replacement sets of seals and gaskets available for engines.

72-60-02e6 Mandatory Replacement of Parts

It is required that certain parts throughout the engine, including the following, be
replaced at overhaul regardless of their apparent condition:

● All engine oil hoses

● All engine hose assemblies

● All oil seals

● All cylinder base seals

● All gaskets

● Piston rings

● Piston pin plugs

● All intake and exhaust valve retaining keys

● All exhaust valve retaining rings

● Cylinder fin stabilizers

● Magneto drive cushions

● Magneto isolation drive bearings

● Thermostatic bypass valves

● Damaged ignition cables

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Section 72-60-02 IO-390-A Series Maintenance and Overhaul Manual

● Counterweight bushings in crankshaft and in counterweights

● Fuel pump plunger for diaphragm fuel pumps

● Hydraulic roller tappets

Any time the following parts are removed from an engine, or at overhaul, it is
mandatory that the parts be replaced regardless of their apparent condition.

● All circlips, lockplates, retaining rings

● All counterweight washers

● All lockwashers and locknuts

● All main and connecting rod bearings (may also be referred to as “bearing
inserts”)

● Stressed bolts and fasteners, such as:

● Camshaft gear attaching bolts

● Connecting rod bolts and nuts

● Crankshaft flange bolts

● Crankshaft gear bolts

72-60-02e7 Fuel Supply System

The fuel supply lines to the nozzles can become damaged and will leak if not
properly installed and clamped at the correct locations. See Figure 72-60-08-2.

Caution
Do not attempt to repair a damaged fuel line. Replace any line that is
cracked, dented, or kinked. Cracks can develop at the site of sharp bends
or kinks.

Caution
Never use a sharp tool such as a wire or pin to clean out a fuel nozzle.
Damage to the inlet and outlet fuel restrictors could result.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-03

72-60-03 OVERHAUL OF THE IGNITION SYSTEM

72-60-03a General
The Lycoming IO-390-A Series engine is equipped with a high-tension ignition
system which delivers high-tension current directly to the spark plug outlets.

Dual ignition is furnished by two Slick magnetos.

The firing order for this engine is 1-3-2-4.

The ignition harnesses are composed of a magneto terminal assembly, the

ignition cable, and the spark plug end assembly.

72-60-03b Removal

72-60-03b1 Ignition Harness

Refer to Figure 72-60-03-1.

Lycoming recommends that the ignition harness be replaced at every overhaul.

12. Remove the leads from the spark plugs and disconnect the clamps attaching
the harness to the engine.

13. Remove the 3 screws which attach the harness cap (8) to the magneto, and
remove the harness.

72-60-03b2 Magnetos

14. Refer to Figure 72-60-03-1 to remove magneto from the accessory housing.

15. Remove the P-lead wires which connect to the magneto.

16. Remove the nuts (12), lockwashers (10), washers (11), and mounting
brackets (9) that secure the magneto to the accessory housing.

17. Remove the magnetos (7), magneto adapters (5), and gaskets (4).

Revised June 2009 Page 19, Section 72-60

Section 72-60-03 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-03-1. Slick Magneto Drive Assembly

Note: The gears mentioned in the next step are part of the accessory drive and
should not be considered as part of the ignition system. Their removal
and reassembly is discussed in this section because they must be
removed and reassembled at the same time the magnetos are removed
and reassembled.

5. Reach inside the drive pad and remove the drive cushions (1), magneto gears
and cushion retainers (2), and ball bearings (3).

72-60-03c Replacement
Magneto is not repairable. Replace with a serviceable part.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-03

72-60-03d Reassembly

72-60-03d1 Magnetos

1. Refer to Figure 72-60-03-1.

2. Assemble the gaskets (4), and adapters (5) on the magneto mounting pad.

3. Place the ball bearing (3) on the magneto gear and cushion retainer (2).

4. Insert the cushions (1) in the cushion retainer.

5. Refer to figure 72-60-03-2. Install the assemblies engaging the marked tooth
of the magneto gear.

Figure 72-60-03-2. Marked Teeth on Crankshaft Idler Gear

72-60-03d2 Installing the Magneto Drive Gear

1. Install the magneto drive gear onto the magneto rotor shaft or impulse
coupling.

2. Place the washer onto the shaft and drive gear.

3. Place the nut onto the rotor shaft and torque to 120 to 130 in.-lbs.

4. Insert the cotter pin through the nut castellations and rotor shaft and secure
appropriately.

Note: To align the cotter pin with the pin hole it is permissible to continue
tightening the nut to a maximum torque of 300 in.-lbs.

August 2008 Page 21, Section 72-60

Section 72-60-03 IO-390-A1A6 Maintenance and Overhaul Manual

Caution

The magneto will produce spark voltage when the shaft is turned. Keep
your hands away from the distributor block and the condenser stud when
rotating the magneto shaft.

72-60-03d3 Aligning the Magneto Rotor Shaft to Fire Cylinder #1

1. Insert the T-118 timing pin in the left or right hole of the distributor block,
depending on the rotation of the magneto. Refer to the data plate to
determine the normal magneto rotation direction.

2. Turn the rotor shaft in the direction opposite to that specified as the direction
of rotation until the timing pin is inserted to the shoulder of the pin or 7/8 in.
into the distributor block. When properly engaged, the timing pin will seat
against the distributor block.

Note: If the rotor shaft cannot be turned, and the timing pin is not seated 7/8 in.
into the distributor block, remove the pin, give the rotor shaft a 1/8 turn,
and reinsert the timing pin. Repeat steps 1 and 2.

3. With the timing pin fully inserted in the distributor block, the magneto is
aligned to fire cylinder #1.

Caution
Do not rotate the magneto rotor shaft with the timing pin inserted into the
magneto distributor block. Rotation of the rotor shaft in this situation
may damage the internal components of the magneto and render the unit
non-airworthy.

72-60-03e Adjustments

72-60-03e1 Timing Magneto to Engine

1. Turn the crankshaft clockwise until cylinder number 1 is on the compression

stroke and at approximately 35° before top center (BTC).

2. Clamp the ignition timing pointer on the advance timing mark on the rear of
the starter ring gear. The starter ring gear may be marked at 20° and 25°.
Consult the engine nameplate for the correct advance timing mark to use.

3. Continue rotating the crankshaft until the timing pointer and the parting
flange of the crankcase align.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-03

Note: In the event that an ignition timing pointer is not available, use the
following alternate method.

a. Rotate the crankshaft in the normal direction of rotation until cylinder

number 1 is on the compression stroke.

b. Continue to rotate the crankshaft until the correct advance timing mark
on the front of the starter ring gear is in exact alignment with the small
drilled hole located at the two o’clock position on the front face of the
starter housing.

4. Keep the crankshaft in this position until the magnetos are installed.

5. Install the magneto onto the engine.

Caution
Do not rotate the magneto or propeller with the timing pin inserted into
the distributor block. Rotation of the rotor shaft of the propeller in this
situation may damage the internal components of the magneto and render
the unit non-airworthy.

6. Secure the magneto using P/N 66M21195 mounting clamps and appropriate
nuts or bolts. Tighten the nuts or bolts sufficiently to hold the magneto
loosely in position.

7. Remove the timing pin from the distributor block.

8. Attach a timing light to the magneto condenser stud according to the timing
light manufacturer’s instructions.

9. Rotate the magneto in the direction of normal rotation until the timing light
indicates that the breaker points are open. Refer to the data plate to determine
the normal rotation direction. Most timing lights indicate open points with a
light or an audible signal.

10. Slowly rotate the magneto in the direction opposite to that of normal rotation
until the light goes out or the audible signal stops.

11. Tighten the magneto mounting clamps to secure the magneto to the engine

a. Alternately tighten the engine mounting clamp nuts to 8 ft.-lbs. of torque.

b. Continue to alternately tighten both nuts, using several steps, to 17 ft.-

lbs. of torque.

August 2008 Page 23, Section 72-60

Section 72-60-03 IO-390-A1A6 Maintenance and Overhaul Manual

12. Turn the engine 20° opposite direction of rotation, then back in direction of
rotation until the light indicates the points are open. Verify timing marks are
properly aligned.

Caution
In no case should 17 ft.-lbs. be exceeded. If the mounting nuts are
torqued in excess of 17 ft.-lbs., damage to the magneto mounting flange
may result, rendering the unit non-airworthy.

13. Remove the timing light from the magneto condenser stud.

72-60-03e2 Ignition Harness

1. Attach each ignition harness to the appropriate magneto. The left harness is
marked “left” and should be attached to the left magneto on the engine. The
right harness is marked “right” and should be attached to the right magneto
on the engine.

2. Torque the mounting cap screws to 18 to 20 in.-lbs.

3. Refer to Figure 72-60-03-3.

4. Connect the ignition harnesses to the spark plugs as shown.

5. Route the ignition leads to the appropriate spark plug position as indicated by
the alpha-numeric markings on each spark plug nut.
Note: Each spark plug ignition harness nut is marked with a letter and number
code identifying the spark plug position on each respective cylinder. A
spark plug nut marked “T1” identifies the top spark plug on cylinder #1
to which that ignition lead is to be connected. A spark plug nut marked
“B4” identifies the bottom spark plug on cylinder #4 to which that
ignition lead is to be connected.

6. Route the lead wires according to the airframe manufacturer’s instructions.

Position the lead wires to prevent chafing by baffling or engine parts.

7. Install the spark plug nut onto the spark plug and torque the nut 80 to 90 in.-
lbs. for 5/8-24 hardware or 110 to 120 in.-lbs. for 3/4-20 hardware.

Note: When installed, a hex ferrule will protrude above the spark plug
mounting nut. This hex ferrule should be held with a 7/16 in. wrench
while tightening the spark plug nuts to prevent twisting of the ignition
lead.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-03

Figure 72-60-03-3. Ignition Wiring Diagram

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Page 26, Section 72-60 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-04

72-60-04 OVERHAUL OF THE ACCESSORY HOUSING

Remove the magnetos and all accessories from the accessory housing. Remove
attaching hardware and remove accessories.

72-60-04a Disassembly

72-60-04a1 Fuel Pump

Refer to Figure 72-60-04-1.

Figure 72-60-04-1. Fuel Pump Assembly

1. Remove four nuts and washers that secure the fuel pump to the accessory
housing.

2. Remove the fuel pump.

3. Remove the gaskets and discard them according to all applicable federal,
state, and local environmental regulations.

72-60-04a2 Accessory Drive Assembly

Vacuum Pump Drive. Refer to Figure 72-60-04-2.

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Section 72-60-04 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-04-2. Accessory Drive Adapters

1. Remove the nuts (11), lockwashers (10), and plain washers (9) from the plate
on the upper right side of the accessory housing.

2. Remove the adapter assembly from the accessory housing.

3. Remove the driven gear (5), washer (6) and seal (3).

Propeller Governor Drive.

1. Refer to Figure 72-60-06-5. Remove the propeller governor oil line (1).

2. Refer to Figure 72-60-04-2. Remove the adapter (15) from the mounting pad
on lower right side of the accessory housing.

3. Remove the retaining ring (16), washer (13) from shaft gear and remove
shaft gear (12) from adapter (15).

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-04

74-60-04a3 Oil Filter

The oil filter for this engine is a “screw-on, screw-off” unit. Replace the oil filter,
as required, for regularly scheduled maintenance and at overhaul.

1. Unscrew the oil filter from the oil filter base assembly.

2. Remove the oil filter base and gasket.

3. Discard the gasket and oil filter according to all applicable federal, state, and
local environmental regulations.

74-60-04a4 Removing the Accessory Housing from the Engine

Refer to Figure 72-60-04-3.

1. Remove the washers, lockwashers, and bolts that hold the accessory housing
to the engine and the oil sump.

2. Lay the accessory housing on a bench with the inner surface face up on the
bench to prevent dropping loose gears.

74-60-04a5 Oil Pump

Refer to Figure 72-60-04-3.

1. Remove the oil pump drive gear shaft.

2. Remove the lockwire from the slotted nuts on the oil pump.

3. Remove the slotted nuts and washers holding the oil pump body to the
accessory housing.

4. Detach the oil pump impellers.

74-60-04a6 Oil Cooler Bypass Valve

Remove the thermostatic bypass valve from the oil filter base and discard gasket.

August 2008 Page 29, Section 72-60

Section 72-60-04 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-04-3. Oil Pump Assembly and Accessory Housing Attaching Parts

72-60-04b Cleaning

72-60-04b1 Accessory Housing Parts

Remove all parts, plugs, fittings, seals, and gaskets from the accessory housing.
Clean all parts of the accessory housing according to the general cleaning
instructions given in section 72-60-02b.

72-60-04c Inspection
Inspect all parts of the accessory housing according to the general inspection
procedures given in section 72-60-02c. Refer to Table of Limits Section,
Appendix III, for components and inspection criteria.

72-60-04d Repair and Replacement

Replace all gaskets, oil seals, circlips, and retaining rings during reassembly.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-04

72-60-04e Reassembly

72-60-04e1 Oil Pump

Refer to Figure 72-60-04-3.

1. Lubricate all parts with a mixture of 15% pre-lubricant and 85% SAE No. 50
mineral base aviation grade lubricating oil.

2. Install the impellers in the body.

3. Insert the oil pump drive gear shaft into the body and through the drive
impeller.

4. Install the assembly over the mounting studs on the accessory housing.

5. Place a washer and slotted nut on each stud.

6. Tighten the nuts gradually and evenly, turning the drive gear shaft while
tightening to ensure free movement of the impellers.

7. Tighten the nuts to 17 ft.-lbs.

8. Lockwire according to section 70-00-02.

72-60-04e2 Accessory Housing Installation

Refer to Figure 72-60-04-3.

1. Place a new accessory housing gasket over the locating dowels on the rear of
the crankcase. (See Figure 72-60-04-3.)

2. Apply a liberal coating of engine oil to the tachometer drive shaft and all
other contact surfaces, such as gear teeth and the idler gear hub.

3. Assemble the tachometer drive oil seal to the outside of the accessory
housing.

4. Guide the accessory housing over the tachometer drive shaft and then onto
the locating dowels.

5. Fit the accessory housing into place on the rear of the crankcase.

6. Secure the housing in place.

7. Assemble all bolts with plain washers and lockwashers. Refer to Table of
Limits for torque values.

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Section 72-60-04 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-04e3 Vacuum Pump Drive Installation

Refer to Figure 72-60-04-2.

1. Insert a new oil seal (3) into the recess in the vacuum pump adapter (2).

2. Place a new accessory driven gear washer (6) over the shaft of the vacuum
pump-driven gear (5).

3. Lubricate the shaft with Lubrico M-6 Grease or equivalent.

4. Insert the gear into the adapter, being careful not to push the oil seal out of its
seat.

5. Using a new gasket (1), attach the adapter to the upper right side of the
accessory housing with four plain washers (9), lockwashers (10), and nuts
(11).

6. Place a cover (8) and gasket (7) over the exposed end of the drive to prevent
the entrance of dirt and/or other foreign matter.

72-60-04e4 Fuel Pump

Refer to Figure 72-60-04-1.

1. Lubricate the shaft of the fuel pump with Lubriko grease (manufactured by
Lubriko Lubricants) or equivalent.

2. Install a new gasket onto the fuel pump and insert the fuel pump assembly
into the accessory housing.

3. Apply Loctite 564 to the bolts. Secure the assembly with washers and torque
to 25 ft.-lbs.

72-60-04e5 Oil Filter and Filter Base

1. Install a new gasket on the pad.

2. Install the oil filter base.

3. Install 3 each ¼ x 20 nuts with flat washers against accessory housing, then
lock washers.

4. Install cap screw.

5. Torque all hardware in accordance with Table of Limits

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-04

72-60-04e6 Oil Cooler Bypass Valve

Install new gasket; install valve into oil filter base and torque in accordance with
Table of Limits.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-05

72-60-05 OVERHAUL OF THE CYLINDERS, PISTONS, AND VALVE TRAIN

72-60-05a General Information

For overhaul purposes, the pistons belong with the cylinders because the basic
configuration of the engine requires the removal and reassembly of the pistons at
the same time that the cylinders are removed or replaced. Similarly, the valve
train includes all parts of the valve-operating mechanism beyond the camshaft,
beginning with the hydraulic tappet assembly.

The IO-390-A Series engine has nitride-hardened steel cylinders, which is

indicated by the blue color code shown on the cylinder fins below the spark plug
hole. The yellow color located on the fins above the spark plug hole indicates
that “long reach” spark plugs are required for this engine.

Figure 72-60-05-1. Angle Valve Cylinder Assembly

72-60-05b Cylinder Assembly Removal

Remove the ignition harness (72-60-03b-1), intake pipes (72-60-07b1), fuel
injector (72-60-07b2), and fuel injection lines (72-60-08b1) from the engine.

Revised June 2009 Page 35, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

1. Remove oil drainback tubes.

a. Disconnect tube at cylinder by loosening the flange nut that connects the
tube to the elbow in the cylinder.

b. Disconnect at crankcase by loosening the hose clamps closest to the

crankcase.

c. Remove hose from nipple in crankcase.

2. Remove the intercylinder baffles using the intercylinder baffle tool (P/N
64885)

a. Turn the baffle retainer hook so that it disengages the retainer

b. Remove the intercylinder baffle and hook from between the cylinders.

3. Remove the cylinder assemblies :

a. Remove the rocker box covers and gaskets.

b. Remove the rocker shaft covers and gaskets.

c. Rotate the crankshaft to place the piston in the Number 1 cylinder at the
TDC of the compression stroke. (With the piston in this position, both
intake and exhaust valves are closed and the piston is extended away
from the crankcase to prevent damage when the cylinder is removed.)

d. Push the valve rocker shafts outward to allow clearance for the removal
of valve rockers and valve rocker thrust washers.

e. Remove push rods and the valve stem caps.

Caution
Do not attempt to remove valve rocker shafts until the cylinder is
removed.

4. Using the shroud tube wrench (ST-142), turn each shroud tube 90° in either
direction to release the detent on the tube from the spring.

5. Remove the shroud tubes by first releasing them from the seal seats and in
the cylinder heads and withdrawing the tubes.

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6. Remove the seals from the ends of the shroud tubes.

7. Remove the seals from the crankcase. Discard all seals.

8. Remove the seats and springs and place them in the cleaning basket.

9. Remove the hex head cylinder base hold-down nuts.

Caution

As each cylinder is separated from the crankcase, catch and hold the
piston to prevent it from falling against the crankcase and being
damaged.

10. Remove the cylinders in the order 1-3-2-4 to minimize turning the
crankshaft.

11. Remove the cylinder base oil seal rings and set them aside to use as supports
for the connecting rods after the pistons are removed.

12. Remove the pistons by first removing the piston pin plugs in the order
1-3-2-4 using a piston pin puller (P/N 64843). As each piston pin is removed,
the piston is separated from the connecting rod.

Caution
Refer to Figure 72-60-05-2. When the piston is separated from the
connecting rod, the connecting rod must be supported to prevent damage
to the rod and the crankcase. Use torque hold-down plates (ST-222) or
loop the cylinder base oil seal rings around the cylinder base studs and
connecting rods.

Figure 72-60-05-2. Two Methods of Supporting Connecting Rods

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13. Refer to Figure 72-60-05-4. Remove the hydraulic tappet plungers using the
hydraulic tappet tool (P/N 64941).

Caution
It is imperative that the various parts of each tappet assembly be kept
together during all overhaul operations. This will ensure that all
component parts may be reassembled with their original mating parts and
that each completed assembly is inserted into its original location in the
crankcase.

Caution
If a hydraulic tappet tool is not available, remove the push rod sockets by
hand or by fashioning a loop from a short length of safety wire. Do not
use a magnet to remove the socket or the plunger assembly from the
engine, as this could cause the ball to remain off its seat and make the
unit inoperative.

a. Refer to Figure 72-60-05-3. Remove the push rod socket by placing

heavy grease on the ball end of the “T.” Insert the ball end into the socket
and withdraw it. The socket will adhere to the grease.

b. Push the hollow end of the tool over the hydraulic tappet plunger and
withdraw the plunger.

c. Bend a right angle in one end of a piece of wire and insert this end into
the space between the plunger assembly and the tappet body. Turn the
wire 90° to engage a coil of the spring and draw out the hydraulic tappet
plunger assembly. Refer to Figure 72-60-05-4.

Figure 72-60-05-4.
Figure 72-60-05-3.
Removing Hydraulic Tappet
Removing Push Rod Socket
Plunger Assembly

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72-60-05c Disassembly

1. Place the cylinder over a cylinder holding block (P/N 64526-2 or equivalent)
and assemble the valve spring compressor (ST-25) on the cylinder. Compress
the valve springs far enough to remove the valve retaining keys.

Note: If the keys are stuck tightly in the spring seat, a light blow with a leather
mallet on top of the valve spring compressor will release the keys.

a. Remove all valve spring seats and springs from the rocker boxes,
keeping the parts for each valve separate.

b. Hold valves by the stems to keep them from dropping out of the cylinder.

c. Remove the cylinder from the holding block.

d. Reach inside the cylinder and remove the valves. If difficulty is

experienced in pulling the tops of the valve stems through the valve
guides, push the valves back into position and clean any carbon from the
valve stems.

Caution
Do not force the valves through the guides.

e. Place each valve with its spring, seat, and key in the proper compartment
of the cleaning and inspection basket (P/N 64553). No further
disassembly of the cylinder is necessary unless inspection warrants the
replacement of valve guides or valve seats.

2. Use the piston ring expander (P/N 64713) to remove the rings from all
pistons, starting with the top ring and working down the length of the piston,
being careful not to scratch or score the piston when removing the rings.

3. Disassemble the hydraulic roller tappets. Refer to Figure 72-60-05-5.

a. Push the spring end of the hydraulic tappet plunger. Turn it clockwise
approximately one-quarter turn.

b. Pull it from the cylinder.

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Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-05-5. Hydraulic Roller Tappets

Caution
Keep the plunger and cylinder of each tappet assembly together. They
are very closely and selectively fitted together during manufacture and
are not interchangeable.

72-60-05d Cleaning
Clean all cylinder, piston, and valve train parts in accordance with the “Standard
Practices for Overhaul” provided in section 72-60-02. Specific instructions for
hydraulic tappets follow. Specific cleaning instructions for pistons are in Section
72-60-05e5.

Caution
It is imperative that the various parts of each tappet assembly be kept
together during overhaul operations to ensure that all component parts
are assembled with their original mating parts, and that each assembly is
inserted into its original location in the crankcase. In the event that parts
become intermixed, discard them and install new assemblies.

72-60-05d1 Hydraulic Roller Tappets

1. Use the separate compartments in the cleaning basket (P/N 64553) to keep
the valve-operating mechanisms separate. Dip the basket, with all parts
contained in their proper compartments, into a petroleum-based solvent.

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2. Hold the ball check valve in each plunger cylinder off its seat by inserting a
light copper wire, or other relatively soft material, through the tube on the
cylinder and wash it thoroughly so that any dirt particles that may be under
the ball seat will be washed out.

3. After washing each part of the hydraulic tappet assembly, replace the part in
the proper compartment of the cleaning basket.

72-60-05e Inspection
Inspect all cylinder, piston, and valve train parts in accordance with the
“Standard Practices for Overhaul” provided in section 72-60-02. Specific
instructions for each component follow.

72-60-05e1 Cylinder Head (Visual Inspection)

Examine the cylinder head thoroughly. Check for the following possible defects.

1. Loose, scored, pitted, or otherwise damaged valve seats. Replace.

2. Loose or damaged studs. Replace with 0.003, 0.005, 0.007, or 0.012 in.
oversize studs.

3. Loose or damaged spark plug Heli-coil inserts. Replace with oversize insert.

4. Loose, cracked, or scored valve guides. Replace.

5. Nicked, scored, or dented mounting pads for intake and exhaust ports or for
rocker box covers. Replace.

6. Cracked cooling fins. If a cooling fin adjacent to the exhaust port flange is
cracked, a 3/16 in. diameter hole may be drilled as a stop, providing:

a. The end of the crack is at least ¼ in. from the base of the metal; or

b. The cracked area may be removed from the fin, providing that the
maximum removal is no more than one-half the total fin width; or

c. The maximum removal is in accordance with Figure 72-60-05-6; or

d. No burrs or sharp edges are in evidence; or

e. The minimum fillet at the root of the removed portion of the fin is ¼ in.
radius, and the minimum corner at top of fin adjacent to the removed
portion is ½ in. radius; or

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Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-05-6. Maximum Fin Removal

f. The maximum removal is in accordance with Figure 72-60-05-6; or

g. No burrs or sharp edges are in evidence; or

h. The minimum fillet at the root of the removed portion of the fin is ¼ in.
radius, and the minimum corner at top of fin adjacent to the removed
portion is ½ in. radius; or

i. There is no more than one crack per fin, and its depth is no closer than
¼ in. from the base of the metal, and a fin stabilizer is used to reduce
vibration and further deepen the crack.

7. Physically damaged, broken, or bent fins. If a cooling fin is damaged,

broken, or bent, the blended area must not exceed 3/8 in2. nor be 3/8 in. deep;
or

a. No more than four blended fins on the push rod side of the head.

b. No more than six blended fins on the anti-push rod side of the head.

8. In addition to the above, a fluorescent penetrant inspection of the cylinder

must be made. Pay particular attention to the areas between the 15th and 20th
cylinder fins (counting from the top) on the exhaust port side of the cylinder
and the area around the lower spark plug counterbore.

72-60-05e2 Cylinder Head (Dimensional Inspection)

1. Check the ID of the rocker shaft bushings in the cylinder heads using the flat
plug rejection gage (P/N 64613).

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Note: Be sure to use the end of the gage marked “Cyl. Head.”

2. Check for out-of-roundness by trying the gage at several different points on

each diameter being checked.

72-60-05e3 Cylinder Barrel (Visual Inspection)

Thoroughly inspect the cylinder barrel to ascertain its general condition. Make
the following specific checks.

1. Cylinder barrel–Replace any cracked cylinder barrel.

2. Cylinder skirt–Replace any cylinder having a bent, cracked, or broken skirt.

3. Mounting flange–Check for cracks, nicks, or warping. If evidence of cracks,

nicks, or warping is evident, replace the cylinder barrel.

4. Interior of barrel–Inspect for barrel glaze and a possible wear ring “step” at
the point where the piston reverses its travel at the top of the stroke. Barrel
glaze or varnish on the cylinder barrel wall surface must be removed.

a. Use a self-centering, self-bottoming hone that follows a choke located in

the top of the cylinder barrel (Snap-On Tool Co. hone P/N CF-60C with
CF-60C-1 abrasive cloth, or hone P/N CF-60S fitted with CF-61-12S
medium grit stones or the equivalent of these items).

b. Use kerosene or light engine oil for lubrication while honing.

c. Place the deglazing hone in a low-speed drill.

d. Surface hone each cylinder barrel with a minimum of six to eight passes
over the glazed surface, using a smooth up and down motion of the hone
to achieve a good cross-hatch pattern on the cylinder barrel wall.

e. Thoroughly clean the hone of abrasive before going on to hone any other
cylinders.

f. Wipe as much of the abrasive build-up from the cylinder walls and
recesses as possible, paying particular attention to the recesses formed by
the top of the cylinder barrel and the bottom of the cylinder head. Refer
to Figure 72-60-05-7.

g. Fabricate a hooked tool from soft wire and run the tool around in the
recess to loosen any built-up abrasive. This operation must be performed
each time the cylinder is flushed. No abrasive must remain in this area.

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Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-05-7. Section Through Cylinder Assembly Showing Locations

for Diameter Checking and Removal of Wear Step

h. Clean the cylinder by flushing it with a hydrocarbon-based solvent

(Varsol or equivalent). Use the solvent under air pressure. Use a soft
bristle brush in conjunction with flushing to remove abrasive build-up
from areas that are otherwise difficult to reach.

i. Wipe out the cylinder with a clean, white cloth dipped in SAE 10 engine
oil. Examine the cloth under a light for evidence of any abrasive residue
remaining in the cylinder. If any residual abrasive is found, repeat the
above steps until no abrasive residue is found.

j. Oil the cylinder thoroughly with SAE 50 engine oil or a rust preventative
oil that conforms with MIL-C-6529.

Note: If a wear step is detected inside the cylinder barrel, measure it using the
dial bore gage usually used for measuring cylinder diameter. If the depth
of the wear step is less than 0.0025 in., remove the step following the
above procedure for removing cylinder barrel glaze. If the barrel contains
a wear step exceeding 0.0025 in., the cylinder should be replaced.

Note: In some cylinders, a small rough area may be found at either end of the
barrel extending less than 0.250 in. from the end. This condition is a

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result of the manufacturing process and has no effect on the quality or

condition of the barrel.

72-60-05e4 Cylinder Barrel (Dimensional Inspection)

Dimensional inspection of the barrel is provided in the Table of Limits. Make the
following measurements:

● Fit between piston skirt and cylinder

● Maximum taper of cylinder walls

● Maximum out-of-roundness

● Bore diameter

Note: All measurements of cylinder barrel diameters must be taken at a

minimum of two positions 90° apart in the particular plane being
measured. All measurements must be made in the straight portion below
the starting point of the choke or at least 2 in. below the top of the barrel.

72-60-05e5 Piston Cleaning

Using a commercially available solvent, clean piston to remove carbon. Check
and clean the grooves as outlined in Section 72-60-02b.

72-60-05e6 Piston (Visual Inspection)

Examine the top of the piston for pitting, cavities, or surface distortion. If surface
distortion is present, it could be indicative of detonation or pre-ignition. Also,
examine the piston ring lands and grooves, piston pin holes, and piston pin hole
bosses.

72-60-05e7 Piston (Dimensional Inspection)

Refer to Figure 72-60-05-8. Make the following dimensional checks on each
piston.

● Side clearance between piston rings and piston

Note: When checking piston ring side clearance, be sure there are no rolled
edges into the piston ring grooves.

● ID of piston pin hole

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Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

● Clearance between piston skirt and cylinder

● Piston diameter at the top and bottom

Figure 72-60-05-8. Figure 72-60-05-9.

Method of Checking Piston Ring Area to Inspect on Valve Stems
Side Clearance

72-60-05e8 Piston Pins and Piston Pin Plugs (Dimensional Inspection)

Make the following dimensional checks.

1. Check the OD of the piston pin against the ID of the piston.

2. Measure the fit between the new piston plugs and piston.

3. Examine the interior surfaces of the piston pin for corrosion or pitting. If any
of the dimensions vary from those specified in the Table of Limits, replace
the piston pin.

72-60-05e9 Valve Rockers

1. Clean with Scotchbrite or equivalent.

2. Replace valve rockers if the tips show any evidence of damage, wear, pitting
or scoring.

72-60-05e10 Valve Rocker Bushings

Check the ID of the rocker bushing at several different positions with a flat plug
rejection gage (P/N 64613) using the end of the gage marked “Rocker Bushing.”
If the gage enters the bushing at any point, replace the bushing.

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72-60-05e11 Push Rods

Inspect push rods for wear or for looseness of the ball ends.

1. If the ball ends are loose, replace the push rods.

2. Check the rod for straightness. Rods must be straight within 0.010 in.
Replace rods that are not straight.

72-60-05e12 Valves
Remove the valves from the cylinder.

1. Visually examine the valves for physical damage and for damage due to
burning or corrosion.

2. Clean the valves to remove any soft carbon and visually reinspect them.

3. Replace any valves that show damage from burning or from corrosion.

Note: Inconel exhaust valves may be reused if they comply with the
inspections and checks that follow.

4. Measure the valve stem diameter at the mid-point of the stem and at the key
end. If the stem measurements differ at these two points, replace the valve.
Inconel valves may be reused if there is less than 0.002 in. difference
between these measurements. If there is a difference greater than 0.002 in.,
replace the Inconel valve. Refer to Figure 72-60-05-9.

Figure 72-60-05-10. Valve Showing Figure 72-60-05-11.

Locations for Checking Run-Out and Section Through Edge of Valve
Section for Measuring Edge Thickness

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Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

5. Check the run-out of the valve face. Refer to Figure 72-60-05-10. Total run-
out exceed 0.0015 in. If the run-out exceeds 0.0015 in., replace the valve.

6. Measure the edge thinness of the intake valve heads. Refer to

Figure 72-60-05-11. If, after refacing, it measures less than the minimum
permissible edge thickness shown in Table 72-60-05A below, replace the
valve.

Table 72-60-05A. Intake Valve Edge Thickness

Intake Valve Part Number Minimum Permissible Edge Thickness

73117 0.075 in.

Note: The edge of intake valves is formed as shown in Figure 72-60-05-11.
The thickness can best be measured with an optical comparator;
however, it can also be measured with sufficient accuracy using a dial
indicator and a surface plate, as shown in Figure 72-60-05-12.

Figure 72-60-05-12. Method of Checking Valve Edge Thickness with a Dial Indicator

7. Use an optical magnifier to examine the valve stem and tip for evidence of
cracks, nicks, tool marks, or any other indications of damage. Replace any
valve having tool marks or nicks of any sort in the keeper area of an exhaust
valve, or valves having other nicks with ragged edges more than 1/16 in. in
length.

Note: If superficial nicks and scratches in the valve indicate that the valve is
cracked, inspect the valve by either the magnetic particle or dye
penetrant method. Dye penetrant procedures must be carried out strictly
within the penetrant manufacturer’s guidelines.

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8. Using an optical magnifier, examine the face and tip of the valve for
evidence of pitting or uneven wear. Minor pitting should be removed by
regrinding. If regrinding does not remove the pitting, replace the valve.

9. Replace any valve that has been operated with a collapsed tappet regardless
of the number of hours on the valve.

10. Use a magnifying glass (minimum 10 power) to check the face of the tappet
body for signs of spalling or pitting, as shown in Figure 72-60-05-13.
Replace any tappet body showing face wear as indicated in the illustration.

Note: When a tappet body is rejected due to spalling, a visual inspection of the
nose of the corresponding cam lobe must be made using a magnifying
glass (minimum 10 power). The camshaft must be replaced if there is any
indication of surface irregularity, distress, or feathering at the edge of the
lobe.

Figure 72-60-05-13. Appearance of Spalling Marks on Face of Hydraulic Tappet Bodies

11. Each tappet face will have one or two Rockwell marks as shown in Figure
72-60-05-14. These marks are not cause for rejection and are not to be
confused with spalling, as shown in Figure 72-60-05-13.

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Figure 72-60-05-14. Rockwell Marks

12. Refer to Figure 72-60-05-15. Examine the interior of the bore in each tappet
body using a small flashlight to illuminate the interior surfaces. Replace the
entire tappet assembly if there is evidence of wear at the interior shoulder
(which serves as a seat for the plunger assembly), or a feathered or chipped
edge around the shoulder.

Figure 72-60-05-15. Appearance of Interior Shoulder in New and Worn Tappet Bodies

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Caution
After inspection, any serviceable tappet body must be installed in the
same position from which it was removed. Never touch the face of a
tappet body with abrasives because early failure will result.

Hydraulic Plunger Assembly

Check the part numbers of the hydraulic plunger assemblies as they are removed
from the engine. Hydraulic plunger assemblies must be used in sets; it is not
permissible to mix assemblies in the same engine.

Caution
All parts of each hydraulic plunger assembly are selectively fitted and
these parts are not interchangeable. Mating parts must be kept together
and not mixed with other assemblies. If there is any possibility that parts
may have become mixed during disassembly, inspection, or cleaning,
install new hydraulic plunger assemblies.

1. Check each hydraulic plunger assembly for chipping around the seating
shoulder as each assembly is removed from the engine. Refer to Figure
72-60-05-16. If chipping is found, replace the assembly.

Figure 72-60-05-16. Chipped Shoulder

2. Line the assemblies up side by side on a flat surface and lay a straight edge
across the shoulder surface. Refer to Figure 72-60-05-17. Replace any
plunger assembly that is more than 1/32 in. below the straight edge.

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Figure 72-60-05-17. Checking Plunger Assembly

3. Visually inspect each plunger assembly body for cracks. Replace the
assembly if cracks are found.

Caution
Do not use magnetic particle testing or inspection methods on the
hydraulic plunger.

4. Clean the hydraulic plunger assembly with Varsol or equivalent clean

solvent. Back flush it with additional clean solvent.

5. Check the plunger assembly for a leaking check valve.

a. Dip the plunger in light machine or engine oil.

b. Hold the hydraulic plunger between the thumb and middle finger in a
vertical position with one hand. Refer to Figure 72-60-05-18.

c. Place the plunger in position so that it just enters the cylinder.

Figure 72-60-05-18. Checking the Hydraulic Plunger Assembly for Leaks

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d. Depress the plunger quickly with the index finger. If the plunger bounces
back, the assembly is satisfactory.

e. Replace the hydraulic plunger assembly when the plunger does not
bounce back but remains collapsed. This is an indication that the ball
check valve is not seating properly.

Note: Whenever an intake or exhaust valve hydraulic plunger assembly is

determined to be defective, the ball check valve is not seating properly.
The valve as well as the hydraulic plunger assembly must be replaced.

6. To assemble the unit, insert a thin, clean bronze wire into the oil inlet hole
and unseat the ball. With the ball off the seat, insert the plunger and twist
clockwise so that the spring catches.

72-60-05e13 Detection of Magnetized Hydraulic Plunger Assemblies

Parts of this plunger assembly may become magnetized and inoperable. Check
the parts for magnetization with a compass or a small iron wire. If the parts are
magnetized, replace them.

72-60-05e14 Valve Springs

Check the condition of all valve springs with a suitable spring tester (Imada
Model DPS-220R or equivalent) using the loads and deflections as given in the
Table of Limits.

72-60-05f Modifications
Any modifications made to this engine without approval from Lycoming could
void the warranty.

72-60-05g Repair and Replacement – Cylinder Assembly

72-60-05g1 Spark Plug Thread Insert

Any spark plug thread inserts that were rejected during inspection must be
removed and replaced.

Removing the Spark Plug Thread Insert

1. Insert the extracting tool (P/N 64595) into the spark plug hole so that the
edges of the tool cut into the top thread of the insert.

2. Rotate the tool counterclockwise to unscrew the insert from the hole.

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Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Replacing the Spark Plug Thread Insert

1. Withdraw the mandrel part of the inserting tool (P/N 64594) beyond the
recessed section of its sleeve.

Note: If the inspection has determined that a spark plug Heli-coil insert must be
replaced with an oversize (0.010 in.) insert, use a 0.010 in. oversize
bottoming tap (P/N 64596-1) with P/N 64594.

2. Place the insert into the recess and advance the mandrel to engage its slotted
end with the tang of the insert.

3. Press the mandrel forward slightly and rotate the mandrel clockwise. This
will engage the insert in the threaded end of the sleeve.

4. Continue to rotate the mandrel while holding the sleeve to secure the insert
firmly on the inserting tool.

5. Continue to rotate the mandrel until the insert is within one-half turn of the
threads on the threaded portion of the sleeve.

6. Screw the insert into the spark plug hole while making sure that the first coil
picks up the first thread. Turn the tool clockwise to advance the insert into
the hole.

7. When the end of the sleeve is approximately 1/16 in. from the face of the
boss, hold the inserting tool tightly by the handle with one hand and, using
the other hand, rotate the sleeve in a counterclockwise direction to free the
left half-turn on the insert.

8. Slide the sleeve toward the top of the mandrel. The end of the insert can be
seen projecting above the boss.

9. Rotate the mandrel in a clockwise direction until the insert disappears from
sight. When this position is reached, withdraw the inserting tool. The top of
the insert will be approximately one-half turn from the face of the boss.

10. Break off the tang of the insert at the notch using needle nose pliers.

11. Use the expanding tool (P/N 64593) to secure the insert firmly in the spark
plug hole.

12. Keep the expansion within the thread gage limits by fixing the stop nut with
the adjusting screw on the expanding tool at 13/16 in. for long-reach spark
plugs.

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13. Assemble the staking sleeve over the mandrel until the mandrel meets the
boss.

14. Lightly strike the top of the staking sleeve with a hammer to impress a
slightly chamfered edge around the periphery of the tapped hole.

15. Remove the staking sleeve and release the adjusting screw.

16. Remove the mandrel from the insert.

72-60-05g2 Valve Seats

Refer to Figure 72-60-05-19.

Removing and Replacing Valve Seats

1. Replace any valve seats that are loose, damaged, or worn to the extent that
they cannot be reground to the correct dimensions.

2. Place the applicable valve seat replacement fixture on a suitable flat surface
and fasten securely.

3. Fabricate a valve seat removal tool as shown in Figure 72-60-05-19.

Figure 72-60-05-19. Valve Seat Removal Tool

4. Heat the cylinder to a temperature of 600°F (315°C).

a. Preheat an oven to 600°F (315°C) and allow the oven temperature to

stabilize.

b. Place the cylinder in the oven for no less than 1 hour.

c. Secure the hot cylinder into the fixture.

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Note: Perform the next three steps as rapidly as possible after removing the
cylinder from the heat.

5. Soak the sponge of the removal tool in cold water.

6. Insert the tool down through the valve seat. The valve seat will shrink and
cling to the sponge.

7. Withdraw the tool, being careful not to cock the valve seat.

8. Measure the ID of the valve seat recess in the cylinder head. Compare the
measurement with the original manufactured diameter of the recess, as given
in the Table of Limits, to determine which oversize seat should be installed.

9. Refer to Table 72-60-05B to select the proper cutter and cutter pilot.

10. Insert the pilot in the cutter and tighten the cutter in the special drive.

11. Install the pilot-cutter assembly in a drill press.

12. Align the pilot with the valve guide hole.

13. Cut the recess in the head to the appropriate size.

Note: Remove no more of the metal from the bottom of the recess than is
necessary to clean up the major diameter.

Note: In the event that the seats are to be cut by hand, install the hand drive
adapter (ST-63) over the special drive (ST-62) and, using a “T” handle,
cut the recesses as described above.

14. Heat the cylinder to 600°F to 650°F (315°C to 343°C) for 1 to 1-1\2 hour and
secure it to the applicable replacement fixture.

15. Place the new seat on the replacement drift and drive the seat into the recess
in the cylinder head by tapping the end of the drift with a hammer.

Note: Whenever a new valve seat is installed, the matching valve guide must
also be replaced to ensure concentric grinding of the new seat.

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Table 72-60-05B. Valve Seat Replacement Tools

Valve Seat Recess Cutter

ID Valve Seat Hole in Cylinder Head Part Number

1.926-1.928 in. ST-54-1, -2, -3*

2.159-2.161 in. ST-55-1, -2, -3*

*-1 indicates 0.010 in. oversize, *-2 indicates 0.020 in. oversize, *-3 indicates 0.030 in. oversize

Valve Seat Recess Cutter Pilot

ID Valve Guide Hole in Cylinder Head Part Number

0.5915-0.5923 in. ST-66-1, -2, -3, -5*

0.6613-0.6623 in. ST-67-1, -2, -3, -5*

*ST-66 is standard, *-1 indicates 0.010 in. oversize, *-2 indicates 0.020 in. oversize,

*-3 indicates 0.030 in. oversize, *-5 indicates 0.005 in. oversize

Valve Seat Replacement Drift

ID of Valve Seat Part Number

1.870-2.060 in. ST-64

1.474-1.730 in. ST-65

Valve Seat Replacement Fixture for Angle Valve Part Number ST-232
Cylinder Heads

Valve Seat Recess Cutter Driver

Used with all ST-series Cutters ST-62

Hand Drive Adapter ST-63

August 2008 Page 57, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Refacing Valves

1. Place the valve into a suitable valve-refacing machine (Snap-On VR-300 or

equivalent).

2. Set refacer to 30° for intake valves and to 45° for exhaust valves.

3. Using a soft #80 grit wheel, remove no more metal than is necessary to clean
pits in the valve face or to correct any apparent warping condition.

4. Using a hand stone while the valve is turning in the refacing machine, round
off any sharp or burred edges left around the valve face after refacing.

72-60-05g3 Valve Guides

Removing and Replacing Valve Guides

1. Remove the nut from the valve guide puller (ST-49) and screw it to the head
of a ¾-16 bolt.

2. Place the retainer of the puller (ST-49) over the valve guide inside of the
rocker box.

3. Insert the ¾-16 bolt into the retainer and valve guide.

4. From the cylinder barrel end, insert the 3/8-24 bolt into the end of the ¾-16
bolt. Tighten the 3/8-24 bolt until it is snug against the valve guide.

5. Turn the nut in the rocker box clockwise until the valve guide is out of the
cylinder head.

6. Check each valve guide hole in the cylinder head with the applicable valve
guide hole plug gage. Refer to Table 72-60-05C.

7. Mount the applicable valve guide replacement fixture on a drill press table.

8. Fasten the cylinder securely in place on the fixture and set the fixture to the
proper angle of the valve being installed (11°45' for intake valve and 12°40'
for exhaust valves).

9. If measurements indicate that the next oversize guide is required, select the
appropriate reamer and mount it in the drill press spindle.

10. Ream the valve guide hole in the cylinder head. Check the hole with the
corresponding gage.

11. Heat the cylinder to 350° to 400°F (177° to 204°C) for a minimum of 1 hour.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

12. Place the new guide on the appropriate valve guide installation drift and
insert the guide in the hole in the cylinder head.

13. Drive the guide to a firm seat with sharp hammer blows on the end of the
drift.

14. Allow the cylinder to cool and ream the ID of the valve guide with the
appropriate valve guide ID reamer.

15. Check the finished ID with the corresponding valve guide ID gage.

Table 72-60-05C. Valve Guide Replacement Tools

Gage Size Reamer

Valve Guide Hole in Cylinder Head (0.5913 to 0.5923 in. hole)

64571 Standard -----
64507 0.005 in. oversize 64678-2
64509 0.010 in. oversize 64678-3
64511 0.020 in. oversize 64678-4
64639 0.030 in. oversize 64678-5

Valve Guide Hole in Cylinder Head (0.6613 to 0.6623 in. hole)

64940 Standard -----
64928 0.005 in. oversize 64924-1
64929 0.010 in. oversize 64924-2
64930 0.020 in. oversize 64924-3
64931 0.030 in. oversize 64924-4

Valve Guide ID
64514 0.4040 to 0.4050 in. exhaust valve 64684

Pilot Diameter
ST-155 0.4995 to 0.5005 in. exhaust valve (Ni-Resist) -----
----- 0.4828 to 0.4833 in. ST-143-1
----- 0.4778 to 0.4783 in. ST-143-2

Replacement Fixture
T/N Cylinder Assembly
64644 All 5-1/8 in. angle valve heads

August 2008 Page 59, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Gage Size Reamer

Replacement Drift
64505 All intake valve guides
64923 Valve guides with 0.4985 to 0.4995 in., 0.4995 to 0.5005 in. ID

Grinding Valve Seats

The ID of the valve guide is used as a piloting surface for all valve seat
reconditioning operations. Grind valve seats, using suitable grinding equipment,
to a 30° angle on intake valves and a 45° angle on exhaust valves.

Figure 72-60-05-20. Valve Seat Dimensions for Reconditioning

1. Intake valve seats – Use a 15° grinding wheel to grind the top surfaces of the
valve seat to produce the outer face diameter of 2.334/2.344 in. Use a 75°
wheel to bring the face of the intake valve seats to narrow the throat to
0.074/0.093 in.

2. Exhaust valve seats – Use a 15° grinding wheel to grind the top surface of
the valve seats to produce the outer face dimension of 1.816/1.826 in. The
width of the exhaust valve seats should be 0.091/0.106 in.

Note: If seat wear has progressed to the extent that the entire face of the 15°
narrowing wheel must be brought into contact with the seat to achieve
the specified diameter, the seat must be replaced. Refer to Figure 72-60-
05-21.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

Figure 72-60-05-21. Rejection of Valve Seat

72-60-05g4 Valve Rocker Thrust Washers
Adjusting Valve Rocker Thrust Washers

1. Measure the clearance between the valve rocker and cylinder head using a
feeler gage.

2. Refer to the Table of Limits. Compare the actual measurements with the
service limit of 0.024 in.

3. Reduce excess clearance caused from excessive wear on the inner rocker
shaft support boss using the inner rocker shaft spotfacer (P/N 64862).

4. Remove no more metal than is necessary.

5. Select and fit any two of the three undersize washers needed to bring the side
clearance within service limits. Refer to Table 72-60-05D.

Table 72-60-05D. Washer Part Numbers and Sizes

Part Number Size Edge Color

71549 (Standard) 0.090 - 0.095 in. none

71549-1 0.049 - 0.051 in light blue

71549-2 0.059 - 0.061 in. white

71549-3 0.064 - 0.066 in. yellow

72-60-05g5 Valve Rocker Shaft Bushings

Replacing the Valve Rocker Shaft Bushing

1. Remove the outer and inner bushing using the rocker shaft bushing removal
drift (P/N 64814).

August 2008 Page 61, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

2. Check each rocker shaft bushing hole in the cylinder heads using a standard
plug gage (P/N 64810). If the plug enters the head more than 1/8 in., an
oversize rocker shaft bushing is required.

Note: If the fit of the plug gage in the hole is quite loose, it is evident that the
bushing removed was an oversize bushing. In that case, use the 0.005 in.
oversize plug gage (P/N 64811) to determine what oversize bushing
should be used for replacement.

3. When the proper size replacement bushing has been determined, place the
pilot of the outer rocker shaft bushing hole into the cylinder head reamer
(P/N 64812 or P/N 64823) through the outer hole into the inner hole of the
head. Ream the outer hole.

4. Place the inner rocker shaft bushing hole in the cylinder head reamer (P/N
64832 or P/N 64833) through the outer hole and ream the inner hole of the
head.

5. Thoroughly clean the cylinder and reamed holes thoroughly using Varsol or
Safety Solvent to remove any chips or other residue from reaming.

6. Place the stop of the outer rocker shaft bushing installation drift (P/N 64815)
between the inner rocker shaft bushing boss and the outer rocker shaft
bushing boss.

7. Assemble the new bushing on the pilot of the inner rocker shaft bushing
installation drift (P/N 64816) and position the bushing and pilot.

8. Insert the drift through the outer bushing into the pilot and tap the inner
bushing into place.

9. Once the new rocker shaft bushing is installed in the cylinder head, ream the
bushing ID.

a. Place the pilot of the outer rocker shaft bushing ID semi-finish reamer
(P/N 1964819) through the outer bushing.

b. Place the inner rocker shaft bushing ID semi-finish reamer (P/N 64820)
through the outer bushing and ream the inner bushing.

c. Repeat the above two steps using the outer and inner finish reamers
(P/N 64821 and P/N 64822).

d. Check the finished ID hole in the rocker shaft bushing with the rocker
shaft bushing ID plug gage (P/N 64823).

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

e. Clean the cylinder and reamed hole thoroughly using Varsol or Safety
solvent to remove any chips or other residue caused from the reaming.

Note: After the bushings have been reamed, they must be impregnated by
immersing them for at least 15 minutes in engine oil that has been heated
to 140°F (60°C). Immerse only the portion of the head containing the
bushings.

10. Place the valve rocker in position in the valve rocker holding fixture (P/N
64540) and, using a suitable drift, remove the bushing from the valve rocker.

11. Position a new bushing into the valve rocker.

12. Align the oil hole in the bushing with the oil hole in the valve rocker.

13. Insert the bushing into the valve rocker using an arbor press.

14. Burnish the bushing by using an arbor press to pass the valve rocker bushing
burnisher (P/N 64541) completely through the bushing.

15. Remove the rocker from the fixture and check the finished ID with the valve
rocker bushing finished ID gage (P/N 64823).

72-60-05g6 Cylinder Barrels

Nitrided Cylinder Barrels

When the nitrided cylinder barrels in the IO-390-A1A6 engine have worn beyond
service limits, they must be replaced. They cannot be repaired.

72-60-05g7 Valve Repair

Repairs to valves are limited to removing carbon, regrinding the face, and
polishing superficial scratches. Bending processes to straighten and puddling to
restore the face must not be attempted. Refer to Section 72-60-02b.

72-60-05g8 Exhaust Flanges

Milling Warped Exhaust Flanges

Straighten any exhaust flanges by milling. A maximum amount of 0.020 in. may
be removed in increments of 0.010 in. The cylinder head should be stamped
adjacent to the port sealing surface with “10” or “20” to indicate the amount of
metal removed.

1. Examine the surface of the exhaust flange face for erosion damage.

August 2008 Page 63, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

2. Remove studs using standard stud removal tool.

3. Mill the exhaust flange face 0.10 in.

4. Reexamine the flange face. If needed, mill an additional 0.010 in. The
maximum removable amount is 0.020 in.

5. Mark “FR10” or “FR20” adjacent to the outboard bolt hole to designate the
amount removed (FR = flange rework).

Note: All exhaust flanges on the same side of the engine must be reworked
equally to prevent cracking on the exhaust pipes near the flange.

72-60-05h Reassembly

72-60-05h1 Assembly of Pistons and Rings

Figure 72-60-05-22. Piston Assembly

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

Assembling Pistons

1. Refer to Figure 72-60-05-22. Using a commercially available piston ring

expander, assemble new rings on the pistons.

Note: The equalizer ring and the regulating ring are symmetrical and may be
installed with either side upward.

2. With the piston lying top side up on a workbench, install the oil regulating
ring equalizer in the first groove above the piston hole.

3. Assemble the oil regulating ring over the equalizer with its gap 180° opposite
the equalizer gap.

4. Compress the assembly several times with the fingers to make sure the rings
lie freely and loosely in the groove.

5. Install compression rings with the word “Top” toward the top of the piston in
the remaining top grooves.

Caution
Do not, under any circumstances, install chrome-plated piston rings in an
engine having chrome-plated cylinder barrels. If you are unsure of the
proper combination of rings to be used, contact the Service Department
at Lycoming.

6. Measure the side clearance of the rings in the grooves. Use a feeler gage and
a straight edge as shown in Figure 72-60-05-8.

7. Compare the actual measurements to those listed in the Table of Limits.

72-60-05h2 Assembly of Cylinders

See Figure 72-60-05-23.

1. Coat the intake valve guide and intake valve with Texaco 140, Kendall 155,
Atlantic-Richfield 165, Lubri-bond MIL-L-23398, Texaco EPO, or
equivalent.

2. Insert the intake valve into the guide.

3. Coat the exhaust valve guide and the exhaust valve with Texaco 140, Kendall
155, Atlantic-Richfield 165, Lubri-bond MIL-L-23398, Texaco EPO, or
equivalent.

4. Insert the exhaust valve into the guide.

August 2008 Page 65, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-05-23. Cylinder Assembly

Note: The intake valve is slightly larger than the exhaust valve.

5. Holding the end of the valve stems, place the cylinder on the cylinder
holding block (P/N 64526-2).

6. Install on the intake valve a lower intake spring seat, an outer valve spring,
an inner valve spring, and an upper valve spring seat.

7. Install on the exhaust valve a lower spring seat, an outer valve spring, an
inner valve spring, and an upper valve spring seat.

Note: Assemble the dampener ends of the springs (closely wound coils marked
with dye or lacquer) downward or next to the lower spring seats.

8. Compress the valve springs with the valve spring compression tool (ST-25).

9. Assemble the intake valve-retaining key and intake valve stem cap.

10. Assemble the exhaust valve-retaining key and exhaust valve stem cap.

Note: If the valve does not seat properly, place a wooden hammer handle
against the tip of the valve stem and strike the hammer head with the
palm of the hand. Do not use any other method to seat the valve.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

72-60-05h3 Installation of Pistons (After Crankcase and Crankshaft Assembly)

1. Remove all preservative oil accumulation from the piston and cylinder
assemblies by washing with Varsol, Safety Solvent, or equivalent solvent
meeting MIL-PD-680 specifications.

2. Thoroughly dry with compressed air.

3. Insert the valve rocker shafts into their bores in the rocker box.

4. Starting with piston Number 1, apply a generous coating of a mixture of 15%

prelubricant (STP or equivalent) and 85% SAE 50 mineral-base aviation-
grade lubricating oil to the inside of the cylinder barrel, to the piston rings,
working the mixture into the ring grooves, and to the ID of the piston pin
holes.

Caution
Do not attempt to rotate the crankshaft unless the connecting rods are
supported.

5. Rotate the crankshaft so that when the Number 1 piston is inserted, it will be
at the TDC of its firing stroke, with both tappets on the base circle of the cam
lobes.

6. Insert the piston so that the number stamped on the bottom of the piston head
is toward the front of the engine.

7. Refer to Figure 72-60-05-22. Insert the piston pin using only palm pressure.

Note: If the original piston pin is tighter than a palm push fit, check for burrs or
slight carbon in the pin bore of the piston. Stone away burrs. Remove
carbon as described in “Carbon Removal.” If a new piston or piston pin
is installed, select a pin (P/N 14J22048) that will give a palm push fit at
60° to 70°F (15° to 20°C).

8. Thoroughly lubricate each piston pin plug with Texaco 140, Kendall 155,
Atlantic-Richfield 165, Lubri-Bond MIL-L-23398, Texaco EPO, or
equivalent.

9. Insert piston pin plugs at each end of the piston pin.

10. Repeat the preceding steps with pistons Number 2 through Number 4.

August 2008 Page 67, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Caution
To ensure the proper assembly of the crankcase halves and to minimize
the possibility of the subsequent loosening of cylinder base nuts, a
definite and specific sequence of tightening all crankcase and cylinder
base nuts must be followed. Ensure that crankcase halves have been
brought together and fastenings secured, as described in section 72-60-
06, before installing cylinders.

72-60-05h4 Installation of Cylinders

Refer to Figure 72-60-05-24.

1. Place a rubber cylinder base oil seal ring (30) around the cylinder base.

Caution
Use only P/N 71481 oil seal ring. Do not use any additional sealant or
gasket material which could deteriorate and result in reduced torque on
the cylinder base studs.

2. Install spacers on the thru-studs where cylinders do not attach. (Use two P/N
74887 spacers at the front on the left side and two P/N 77906 spacers at the
rear of the right side.)

3. Assemble the piston ring compressor (P/N ST-485) over the top piston rings
and install the cylinder over the piston, pushing the piston ring compressor
ahead with the cylinder barrel.

4. As the cylinder barrel approaches the crankcase, catch the piston ring
compressor as it drops off the piston skirt.

5. Lubricate the crankcase thru-stud threads with any one of the following
lubricants or combination of lubricants, before installing the cylinder socket
head hold-down nuts (25) and (26):

● 90% SAE 50W engine oil and 10% STP,

● Parker Thread Lube,

● 60% SAE 30 engine oil and 40% Parker Thread Lube, or

● SAE 30W engine oil.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

Figure 72-60-05-24. Cylinder Reassembly

August 2008 Page 69, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Caution

To ensure uniform loading on the main bearings, it is imperative that the

anchored thru-studs and the free-thru-studs are tightened in a particular
sequence, beginning at the approximate center of the engine and then
progressing evenly to both the front and rear of the engine. Refer to
Figure 72-60-05-25.

Note: Before tightening the free-thru-studs, make sure that they extend equally
from both sides of the crankcase.

a. Tighten the ½-20 socket head nuts on the cylinders in the sequence
shown in Figure 72-60-05-25, using the ½ in. socket head nut wrench
(P/N 64942) to 300 in.-lb. (25 ft.-lb.).

b. Tighten both ends of the free thru-studs simultaneously at the rear of

cylinder Number 2 and at the front of cylinder Number 3.

c. Tighten both ends of the free thru-studs simultaneously at the rear of

cylinder Number 4 and behind cylinder Number 3.

d. Tighten both ends of the free thru-studs simultaneously in front of

cylinder Number 2 and at the front of cylinder Number 1.

6. Using the same sequence as above, retighten the ½ in. thru-studs to 600 in.-
lb. (50 ft.-lb.).

7. Tighten the 3/8 in. nuts at the front main bearing (right-hand side) to 300 in.-
lb. (25 ft.-lb.).

8. Tighten the crankcase fastenings (items 6 through 12 on Figure 72-60-06-45)

as numbered in the sequence shown.

9. Tighten the 3/8 in. nut (designated number 13 on Figure 72-60-06-45) at the
rear camshaft bearing location (right side) to 300 in.-lb. (25 ft.-lb.).

10. Recheck all nuts on the cylinders using the torque wrench to apply the
appropriate torque on each nut for 5 seconds. If the nut does not turn, it is
correctly tightened.

11. Recheck all crankcase fasteners using the torque wrench to apply the
appropriate torque on each fastener for 5 seconds. If the fastener does not
turn, it is correctly tightened.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

Note: Torque values are:

● For 3/8 in. nuts, 300 in.-lb. (25 ft.-lb.),

● For ¼ in. nuts and capscrews, 96 to 108 in.-lb., and

● For ¼ in. shear nuts, 55 to 60 in.-lb.

Note: Any additional crankcase fastenings not specifically called out in this
procedure may be tightened in any sequence using the torque values
shown above.

Figure 72-60-05-25. Sequence of Tightening Cylinder Base Nuts

12. Remove any nicks in the cylinder fins by filing or deburring.

13. Install a vented plug in each spark plug hole to prevent the entrance of
foreign materials, while still permitting the engine to be easily turned by
hand.

14. Refer to Figure 72-60-05-24. Install the hydraulic tappet plunger (29) and
cylinder assemblies with the spring end outward and sockets with concave
end outward in the hydraulic tappet bodies.

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Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

Caution
Be sure there is no oil inside the tappet bodies and that the tappet plunger
and cylinder assemblies are thoroughly clean and dry. Wash any
lubricating or preservative oil (Varsol, Stoddard solution, or equivalent)
from these parts, since tappet assemblies must be absolutely dry to check
tappet clearance.

15. Assemble new shroud tube oil seals (24) in the shroud tube oil seal retainers
in the crankcase.

16. Place new shroud tube seals (22) on the outer end of the two push rod shroud
tubes (23).

17. Place a shroud tube spring (21) over the inner ends of two shroud tubes so
that the detent notches in the spring are approximately 90° removed from the
detents on the tubes.

18. Insert the shroud tube ends through the oil seals in the crankcase.

19. Hold both push rod shroud tubes with the detent at the inner end in the
unlocked position.

20. Insert the outer end of the tubes in the cylinder head rocker box.

21. Ascertain that all rubber seals are inserted squarely.

22. Turn each shroud tube 90° to engage the detents and lock the tubes by
engaging the detents with the notches in the shroud tube spring.

23. Select two push rods (27) and dip them into a mixture of 15% STP or
equivalent and 85% SAE 50 mineral-based aviation-grade lubricating oil.

24. Insert the push rod into the full length of the shroud tube.

25. Press the push rods tightly against the outer end of the shroud tube to test the
spring tension and free travel of the unloaded or dry hydraulic tappet
plungers. Check to see that the springs compress and return.

26. Install the special cap (11) over the exhaust valve stem.

27. Slide the rocker shaft (8) back into position.

28. Install the rocker (9) and thrust washer (34).

29. Repeat with the other rocker arm and thrust washer.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-05

Note: If the clearance between the valve rocker and the cylinder head cannot be
brought within the limits (Refer to the Table of Limits) using the
standard valve rocker thrust washers, clean up the worn valve rocker
support boss following the procedure given in section 72-60-05d and use
any two of the selective fit undersize washers to bring the clearance
within limits.

Caution
Exhaust and intake rocker assemblies are different due to the angle of the
valves. Make sure that the rockers are correctly assembled.

30. Using a valve clearance gage (ST-23), check the dry or unloaded valve tappet
clearance by pushing in on the push rod end of the valve rocker, checking
between the end of the valve rocker and the valve stem tip. Valve rocker
clearance must fall between 0.028 and 0.080 in.
Note: If the push rod clearance is not within the prescribed limits, insert a
longer push rod to decrease the clearance. See Table 72-60-05E for a
listing of push rod part numbers.
Table 72-60-05E. Push Rod Part Numbers and Lengths
Push Rod P/N Approximate Length (In.)
15F19957-51 12.926
15F19957-52 12.953
15F19957-53 12.980
15F19957-54 13.007
15F19957-55 13.034
15F19957-56 13.061
15F21362-17 12.926
15F21362-18 12.953
15F21362-19 12.980
15F21362-20 13.007
15F21362-21 13.034
15F21362-22 13.061
31. Recheck the valve rocker clearance on all cylinders and make any
adjustments as required.

32. Temporarily assemble the rocker shaft covers (6) on the angle valve
cylinders to prevent displacement of the valve rockers.

33. Coat all parts in the valve rocker mechanism with a mixture of 15%
prelubricant (STP or equivalent) and 85% SAE 50 mineral-base aviation-
grade lubricating oil.

34. Assemble the rocker box cover gaskets (5) and covers (4) on each rocker box
and tighten the screws to50 in.-lb.

August 2008 Page 73, Section 72-60

Section 72-60-05 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-05h5 Installation of Cylinder Head Fin Stabilizers

1. Clean the stabilizers and affected fin areas thoroughly with Varsol or
equivalent solvent to remove all traces of grease, dirt, or other foreign matter,
and air dry with compressed air.

2. Apply Dow Corning Silastic 140 adhesive to the fin stabilizers and press the
surfaces together.

72-60-05h6 Installation of Intercylinder Baffles

Refer to Figure 72-60-05-24.

1. Hook the “S-type” retaining hook (2) through the hole in the baffle (1).

2. Place the baffle in position beneath and between the cylinders, running the
hook up between the cylinder barrels.

3. Place a baffle retainer (3) in place between the cylinders and, using a baffle
installation tool (P/N 64885), bring the retainer hook through the slot in the
retainer. The retainer is forced down until the hook comes above the surface
of the retainer far enough to be turned and hooked over the bridge between
the slots in the retainer.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

72-60-06 OVERHAUL OF THE CRANKCASE, CRANKSHAFT, AND

RECIPROCATING PARTS

Figure 72-60-06-1. Crankcase and Related Parts

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Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-06a Preparation

1. Mount engine on overhaul stand.

2. Remove accessories, magnetos, harness, fuel pump, fuel lines, hoses, etc.

3. Remove intake pipes (Refer to Section 72-60-07b1).

4. Remove cylinders (Refer to Section 72-60-05b). Be sure connecting rods are

supported as shown in Figure 72-60-05-2.

5. Remove induction system (Refer to Section 72-60-07b).

6. Remove oil sump. (Refer to Section 72-60-02b4.)

a. Remove all attaching hardware.

b. Separate sump from crankcase assembly.

c. Remove and discard gasket.

d. Remove the oil sump baffle.

7. Remove accessory housing (Refer to Section 74-60-04a).

72-60-06b Crankcase Disassembly

Refer to Figure 72-60-06-1.

72-60-06b1 Starter Ring Gear Support

Remove the starter ring gear support and alternator belt from the crankshaft
propeller flange by tapping lightly with your hand on the rear face of the starter
ring gear support.

72-60-06b2 Crankshaft Gear

1. Refer to Figure 72-60-06-2. Remove the bolt, lockplate, and crankshaft gear
from the crankshaft.

2. Remove all the nuts and bolts from the parting surface of the crankcase.

Caution

Make certain that all the nuts and bolts are removed, including those
located behind the cam gear and those under the sump area. If these nuts
and bolts are not removed prior to separating the crankcase halves with
the pressure plate, crankcase breakage will occur.

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Figure 72-60-06-2. Crankshaft and Associated Parts

3. Remove the crankcase from the overhaul stand and place it on the
workbench.

4. Steps 3 through 6 refer to Figure 73-60-06-3. Remove the oil fill tube.

5. Remove the oil pressure relief valve assembly (5).

6. Remove crankshaft oil seal (8).

7. Using a 64682 slide hammer, an ST-271 crankcase thru-stud puller, on ST-

317 crankcase thru-stud drives or a plastic hammer, remove the eight (8)
thru-studs. Do not allow the crankcase halves to separate until all thru studs
are removed.

8. Place the crankcase on its right side.

9. Refer to Figure 72-60-06-4. Reach through the cylinder pads to wire the
camshaft to the left half of the crankcase.

10. Refer to Figure 72-60-06-6. Reach down through the cylinder pads and push
the left half of each crankshaft bearing (6) and (7) down onto the crankshaft
so they will not fall when the crankcase halves are separated.

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Section 72­60­06 IO­390­A Series Maintenance and Overhaul Manual

Figure 72­60­06­3. IO­390­A Series Crankcase

Figure 72­60­06­4. Illustrative Example of Camshaft Wired to Crankcase Half

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-06

Note: In the left half of the crankcase, the intake tappet for its corresponding
cylinder is located nearest the front of the crankcase. In the right half of
the crankcase, the intake tappet is nearest the rear of the crankcase.

Caution
The various parts of each tappet assembly must be kept together during
all overhaul operations to ensure that all component parts may be
reassembled with their original mating parts and that each completed
assembly is inserted into its original location in the crankcase.
11. Refer to Figure 72-60-06-1. Separate the crankcase by hand or use ST-389
crankcase separating tool and remove the tappets (8), camshaft (3), and
crankshaft assembly (2).
12. Place each tappet body, as it is removed, in the cleaning basket (P/N 64553)
in its separate, labeled compartment.
72-60-06b3 Propeller Governor Drive Removal (Rear of Accessory Housing)
1. Refer to Figure 72-60-06-5. Locate the propeller governor drive on the rear
of the accessory housing.

Figure 72-60-06-5. Propeller Governor Drive (Rear of Accessory Housing)

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Section 72-60-06 IO-390-A Series Maintenance and Overhaul Manual

2. Remove the propeller governor oil line (1).

3. Remove the adapter (13) from the mounting pad on lower right side of the
accessory housing.

4. Remove retaining ring (14), washer (11) from shaft gear and remove shaft
gear (10) from adapter (13).
72-60-06b3a Propeller Governor Drive Removal (Front Left Hand Side of Crankcase)
1. Refer to Figure 72-60-06-5A. Locate the propeller governor drive on the
front left-hand side of the crankcase.

Figure 72-60-06-5A. Propeller Governor Drive (Front Left Hand Side of Crankcase)

2. Remove the hex head plug (10) and gasket (9).

3. Remove the #10-32 x .31 setscrew (8) from the propeller governor idler gear
shaft (2).
Note: The setscrew (8) has been peened or staked into the hole. It will be
necessary to remove the distorted material to remove the setscrew.
4. Support the idler gear assembly (3) to prevent it from being dropped and
damaged and, simultaneously, remove the idler gear shaft (2), idler gear
bushings (4), and thrust washer (7).

5. Pull the governor drive gear (1) away from the crankcase.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-06

72-60-06b4 Crankcase
5. Refer to Figure 72-60-06-6. Remove the threaded plugs from the crankcase
to facilitate cleaning.

Figure 72-60-06-6. Crankcase Assembly

Figure 72-60-06-7. Crankshaft and Coutnerweight Assembly

Revised January 2010 Page 81, Section 72-60

Section 72-60-06 IO-390-A Series Maintenance and Overhaul Manual

2. Remove and discard the rubber oil seals (9).

3. Remove the two crankshaft idler gear shafts from the rear of the crankcase
halves.
72-60-06b5 Crankshaft
1. Steps 1 through 8 refer to Figure 72-60-06-7. Support the crankshaft (1) at
the front and rear main bearings in a suitable V-block-type fixture.

Note: Undersize crankshafts are identified by a code symbol stamped on the

front of the flange as a suffix to the part number. In addition to the code
symbols, the letters "RN" are stamped as a suffix to the serial number,
indicating that the crankshaft has been renitrided.

2. Remove the nuts securing the rod caps to the connecting rod.

Note: Keep rod caps with the rod from which they were removed.
3. Remove the rods by tapping on the rod bolts with a soft (plastic head)
hammer.

Caution
Do not reuse the connecting rod bearings, bolts, and nuts.

4. Reassemble each cap with its corresponding rod.

5. Flatten out the crankshaft lockplate (14) and remove the hex head bolt (15).
Note: Do not remove the dowel from the end of the crankshaft unless damage
is evident.
6. Remove the crankshaft gear (13) from the crankshaft by tapping it gently
with a fiber drift.

7. Remove the crankshaft gear.

Do not remove the propeller flange bushings (3), (4), and (5) unless they are
loose or damage is evident.
8. Cut the crankshaft oil seal and remove it from the crankshaft.

9. If installed, remove the expansion plug (6) from the crankshaft by punching a
1/8 in. to 3/16 in. hole in the center of the plug. Insert a hook or bent rod and
pull out the plug.

Note: The engine is shipped from the factory with the expansion plug installed
in the crankshaft. The plug must be removed when a constant speed
propeller is used.

10. The inner plug (item 2) can be removed by the same process (step 9).

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-06

72-60-06b6 Counterweights
Note: Temporarily mark all counterweights, retaining rings, washers, and
rollers during disassembly to ensure proper identification for reassembly.

Caution
Do not score, scratch, etch or in any way permanently mark any surface
of any counterweight part.
1. Remove the retaining rings (12), washers (11), and rollers (9).
2. Detach the counterweights (7) from the crankshaft lug.
72-60-06c Cleaning
Note: Prior to cleaning identify the source of any suspect stains, marks or
residues. These can be an indication of damage.
1. Clean all crankcase, crankshaft, and reciprocating parts in accordance with
the general cleaning procedures shown in section 72-60-02b. Be sure all
sludge is removed.
2. Clean the inside of all crankpin and main bearing journals and all oil
passages with suitable brushes.
3. Flush all parts thoroughly and clean with Varsol, Stoddard’s Solution, or an
equivalent solvent.

4. Dry all parts with compressed air.

72-60-06c1 Piston Cooling Oil Nozzles
1. Immerse the piston cooling oil nozzles in an oil-based solvent such as Varsol,
Stoddard’s Solution, or an equivalent.
2. Insert a light copper wire (or some other relatively soft material) through the
threaded end of the nozzle and hold the ball check valve off its seat in the
nozzle.
3. Wash the nozzle thoroughly with Varsol, Stoddard’s Solution, or an
equivalent solvent to flush out any dirt particles that may have collected
under the ball seat.
72-60-06d Inspection
Inspect all crankcase, crankshaft, and reciprocating parts in accordance with the
general inspection procedures outlined in section 72-60-02c. Specific instructions
follow.
72-60-06d1 Bearings (Precision type)
No inspection is required for precision-type bearing inserts. Replace all
precision-type bearing inserts used for main crankshaft bearings and connecting
rod bearings.

Revised January 2010 Page 83, Section 72-60

Section 72-60-06 IO-390-A Series Maintenance and Overhaul Manual

72-60-06d2 Crankcase (Visual Inspection)

1. Check carefully for burrs, nicks, cracks, and fretting around the bearing
saddle support webs.

Caution
Fretting is a condition caused by slight friction and stress at the
contacting surfaces of the bearing saddles and, if fretting is overlooked
during overhaul, will result in excessively tight crankshaft bearing fits.
Fretted areas have tiny pit holes and a frosted appearance when
compared with the adjacent shiny unaffected surfaces. If evidence of
fretting, larger than ½ square inch, is present at more than two locations
per crankcase half, the crankcase must be returned to the factory for
rework. Although fretting itself does not appreciably damage the
structure of the metal, the fretting action changes the size of the bearing
saddles sufficiently to cause loose thru-studs, undersize main bearing
bores, and eventual engine failure.

2. Check bearing bores and inspect tang slots for any roughness that would
cause improper seating of the bearing inserts. If any roughness is evident,
carefully stone the rough areas; be careful to remove only the raised areas.

3. Check all drilled holes. Make sure they are open and are free of foreign
material.
4. Perform a dye penetrant inspection of the crankcase to check for cracks.
72-60-06d3 Crankcase (Dimensional Inspection)
1. Locate the idler shaft center from the center of the main bearing bore as
shown in Figure 72-60-06-8.
2. Measure the diameter of the shaft recess in the crankcase. If this dimension
exceeds 0.752 in., mark the recesses for repair.

The following paragraphs on Crankshaft and Camshaft dimensions include other

dimensional requirements for the crankcase.
72-60-06d4 Crankshaft (Visual Inspection)
1. Carefully inspect all surfaces of the shaft for cracks. If any cracks are found,
replace the crankshaft.

2. Check the bearing surfaces for scoring, galling, corrosion, pitting, or other
damage. If damage is found, the shaft must be repaired or replaced. Refer to
section 72-60-06e.

3. Inspect the crankshaft using magnetic particle inspection procedure

performed by a certified operator.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

Figure 72-60-06-8. Location of Idler Shaft Recesses in Crankcase

72-60-06d5 Crankshaft (Dimensional Inspection)

1. Place the crankshaft in V-blocks supported at the locations specified in the

Table of Limits (Appendix III).

2. Use a surface plate and dial indicator to measure the run-out at the center
main bearings. If the indicator reading exceeds the dimensions given in the
Table of Limits, replace the shaft.

3. Measure the run-out of the crankshaft flange. If the indicator reading exceeds
the run-out given in the Table of Limits, replace the shaft.

Caution
Do not attempt to straighten a bent crankshaft. This will result in a
rupture of the nitrided surface of the bearing journals that will cause the
eventual failure of the crankshaft.

4. Install new inserts at all main bearing locations.

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Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

5. Assemble crankcase halves together and temporarily tighten all thru-bolts to

300 in.-lb.

6. Measure the OD of the crankshaft main bearing journals and compare the
resulting measurements with clearances in the Table of Limits.

7. Using new bearing inserts, temporarily assemble the connecting rods and
check the crankpin journal clearances.

8. Make a note of the measurements and compare them with those listed in the
Table of Limits.

9. If the clearances do not fall within the prescribed limits, the shaft must be
reground. (Refer to 72-60-06e2.)

Figure 72-60-06-9. Camshaft with Integral Gears

72-60-06d6 Camshaft (Visual Inspection)

1. Refer to Figure 72-60-06-9. Carefully inspect all surfaces of the camshaft for
cracks, scoring, galling, corrosion, pitting, or other damage, paying particular
attention to the bearing surfaces and cam lobes.

2. If a hydraulic tappet body has been rejected for spalling, carefully inspect the
corresponding cam lobe for evidence of distress, surface irregularity, or
feathering on the edges.

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3. Replace the camshaft if any evidence of distress, surface irregularity, or

feathering at the edge of the cam lobes or bearings is found.
72-60-06d7 Camshaft (Dimensional Inspection)
1. Support the camshaft in V-blocks and check the run-out. Refer to the Table
of Limits for mounting locations and clearance.

2. Measure the diameter of the camshaft bearing journals and check them
against the bearings formed by the crankcase. Refer to the Table of Limits. If
the diameter is not within the prescribed limits, it must be replaced.
72-60-06d8 Connecting Rods (Dimensional Inspection)
1. Discard all connecting rod bolts and nuts. (New bolts and nuts are required at
reassembly.)

2. Check the condition of the bore in the large end for seating of the bearing
inserts.

3. Check the condition of the bore in the small end of the bushing with the
connecting rod bushing plug gage (P/N 64537). If the gage enters the
bushing, replace the bushing.
72-60-06d9 Connecting Rods (Parallelism Check)
Steps 1 through 10 refer to Figure 72-60-06-10.

Figure 72-60-06-10. Checking Parallelism of Connecting Rods

1. Verify that the bearing cap is assembled properly and is tightened securely.

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Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

2. Insert the tapered sleeves of the connecting rod parallelism and squareness
gage (P/N 64530) in the bearing holes in the connecting rod.

3. Place arbors through the sleeves.

4. Place the gage arm on the arbor.

5. Rotate the adjusting screw on the gage arm until it just contacts the arbor.

6. Lock the adjusting screw with the wing nut.

7. Remove the gage arm and place it on the other end of the arbor.

8. Check the distance between arbors. For exact parallelism or alignment, the
distances checked on both sides will be the same.

9. Observe if the adjusting screw just contacts the arbor.

10. Refer to the Table of Limits.

72-60-06d10 Connecting Rods (Squareness Check)

Refer to Figures 72-60-06-10 and 72-60-06-11.

Figure 72-60-06-11. Checking Squareness of Connecting Rods

1. Steps 1 and 2 refer to Figure 72-60-06-10. Remove the gage arm.

2. Leave the sleeves and arbors in place.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

3. Steps 3 through 6 refer to Figure 72-60-06-11. Place the parallel blocks of

the connecting rod parallelism and squareness gage (P/N 64530) on the
surface plate.

4. Place the ends of the arbors on the parallel blocks.

5. Check clearance at the points where the arbors rest on the parallel blocks
using a feeler gage.

6. Compare the clearance between each arbor and the parallel blocks against the
Table of Limits.

72-60-06d11 Crankshaft Counterweight Bushings

1. Refer to Figure 72-60-06-7. Replace all crankshaft counterweight bushings

as directed in section 72-60-06e.

Caution
Failure to replace all crankshaft counterweight bushings can cause
engine failure.

72-60-06d12 Piston Cooling Oil Nozzles

1. Refer to Figure 72-60-06-6. Piston cooling oil nozzles are designed to open
at 37 to 50 psi.

2. Refer to Figure 72-60-06-12. Test the nozzle assemblies for the correct
pressure.

Figure 72-60-06-12. Piston Cooling Nozzle Test

August 2008 Page 89, Section 72-60

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

3. Direct a flow of SAE 10 motor oil, heated to 65° to 90°F (18° to 32°C),
through the nozzles. The oil stream must pass through a 1 in. diameter hole
located on a center line through the nozzle and 4.5 in. from the face of the
nozzle at 50 psi. If nozzle does not meet these criteria, replace.

72-60-06e Repair and Replacement

Follow all general instructions for the repair of all crankcase, crankshaft, and
reciprocating parts as shown in section 72-60-02d. Specific instructions follow
below.

72-60-06e1 Crankcase (Idler Shaft Recesses)

1. If it has been determined during dimensional inspection that the idler shaft
recesses are damaged or worn, set up the crankcase in a suitable boring
machine.

Caution
The rear face of the crankcase must be square with the boring machine
spindle within 0.001 in. per 6 in.

2. Refer to Figure 72-60-06-13. Drill the idler shaft recess 0.7344 in. ID to a
depth of 0.21 in.

3. Ream the hole 0.750 to 0.751 in. to a depth of 0.19 in.

Figure 72-60-06-13. Machining of Crankcase for Idler Shaft Bushings

4. Refer to Figure 72-60-06-14. Make a new crankcase bushing from material

meeting specification AMS-4118 or equivalent.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

a. Make the bushing OD 0.752 to 0.753 in.

b. Make the bushing ID 0.615 to 0.618 in.

c. Make the bushing length 0.17 in.

d. Chamfer one end of the new bushing 45° x 0.02 in.

Figure 72-60-06-14. Detail of Idler Shaft Bushing for Crankcase

5. Install the bushing in the idler shaft recess with the chamfered end
downward. Refer to Figure 72-60-06-15.

Figure 72-60-06-15. Idler Shaft Installation in Crankcase

6. Stake the bushing at four places.

7. Countersink the bushing 90° x 0.72 in. diameter.

8. Finish bore the bushing to a 0.625 to 0.626 in. diameter and to a finished
depth of 0.17 to 0.21 in.

August 2008 Page 91, Section 72-60

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-06e2 Crankshaft (Bearing Surfaces)

1. Observe the code stamped onto the front of the crankshaft flange. The letters
“RN” are stamped as a suffix to the serial number, indicating that the
crankshaft has been renitrided.

2. Use the table below to determine the nominal manufactured specifications of

the bearing journals. Undersize crankshaft bearing journals are identified by
a code symbol stamped on the front of the flange as a suffix to the part
number.

Table 72-60-06A. Crankshaft Undersize Codes

0.003 in. 0.006 in. 0.010 in.

Main Bearing M03M M06M M10M

Journals

Crankpin Bearing M03P M06P M10P

Journals

Both M03MP M06MP M10MP

3. Using a micrometer, measure and record the dimensions.

4. If the actual undersize is between the service limit (0.0015 in. and 0.003 in.),
then do the following:

a. Polish to 0.003 in. undersize.

b. Fit with 0.003 in. bearing insert.

c. Repeat for all bearings.

Caution

Do not allow the lathe speed to exceed 150 rpm at any time during
polishing operations.

Note: Polishing undersize is preferable to grinding undersize because shafts

that are polished do not require renitriding.

Note: If one bearing journal is polished to 0.003 in. or 0.006 in. undersize, all
corresponding journals must be polished to the same size.

5. If the actual undersize is greater than 0.003 in., then do the following:

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

a. Polish to 0.006 in. undersize.

b. Fit with 0.006 in. bearing insert.

c. Repeat for all like bearings.

6. If the actual undersize is greater than 0.006 in., then do the following:

a. Grind to 0.010 in. undersize.

b. Install 0.010 in. undersize bearing insert.

c. Repeat for all like bearings.

Caution
Grinding a crankshaft is a delicate operation requiring adequate grinding
facilities and a great degree of skill. A properly dressed wheel
(Carborundum GA54-J5-V10 or equivalent) must be used with generous
amounts of coolant. Feed the journal or pin very slowly and maintain the
final ground finish during the complete operation.

d. Return the ground 0.006 and 0.010 in. shafts to the factory to be
renitrided.

Caution
Shafts that have been ground undersize to 0.006 or to 0.010 in. must be
renitrided. Differences in grinding wheels can cause cuts in the nitrided
surface on one or more of the journal radii, causing areas of stress
concentration that can become fatigue cracks and ultimately result in a
broken crankshaft.

7. Have the crankshaft inspected by a certified operator using the magnetic

particle method in Section 72-60-02c6. Reject the shaft if any cracks or
checks are detected.

August 2008 Page 93, Section 72-60

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-06-16. Reconditioning Crankshaft Oil Seal Surfaces

72-60-06e3 Crankshaft (Reconditioning Worn Oil Seal Surfaces)

Refer to Figure 72-60-06-16. Recondition any damaged crankshaft oil seal
surfaces.

1. Remove the propeller flange bushings from the crankshaft flange using a
propeller flange bushing tool (ST-115).

2. Temporarily mark the locations of long and short bushings.

Caution
Do not scribe locations on the shaft.

3. Discard the propeller flange bushings.

4. Immerse the crankshaft in a solution of 1 lb. ammonium nitrate dissolved in 1

gal. water to strip the cadmium plating from the propeller flange area and the
oil seal area.

5. Mask the bushing holes in the flange to protect them.

6. Center the crankshaft in an external grinder so that the crankshaft rotates in a

counterclockwise direction when it is viewed from the flange (front) end.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

Note: Dress the grinding wheel on the corner toward the propeller flange to a
0.50 in. radius while on the opposite side, toward the oil slinger, the
wheel must be dressed to a 0.13 in. radius. Both radii must blend
perfectly. Do not permit the side of the wheel to touch the propeller
flange or the face of the oil slinger. Refer to Figure 72-60-06-15.

7. Remove nicks and scratches from the area using a No. 54 grinding wheel.

Caution
Do not exceed 0.005 in. (0.010 in. undersize) depth of the grind.

Caution
Do not exceed 10 micro-in. roughness, as measured using a profilometer,
in the oil seal area before polishing with crocus cloth.

8. Apply crocus cloth at a single location and polish.

Caution
Do not move the crocus cloth while polishing since undesirable spiral
marks will result.

9. Clean the shaft with Varsol, Stoddard’s Solution, or an equivalent to remove

all traces of grinding dust.

Note: Do not plate beyond the 0.13 in. radius.

10. Cadmium plate the flange and the oil seal area of the crankshaft as shown in
Figure 72-60-06-16 according to AMS-2400.

11. Bake the crankshaft at 275°F (135°C) for 5 hours to prevent possible
hydrogen embrittlement.

12. Have the crankshaft examined using magnetic particle testing by a certified
operator for cracks in the cadmium plating that are not visible to the naked
eye.

13. Support the crankshaft in V-blocks at the end of the journals.

14. Measure the run-out at the refinished areas using a dial indicator. Total
indicated run-out must not exceed 0.002 in.

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Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

15. Select new propeller flange bushings.

16. Chill the new propeller flange bushings in an ordinary refrigerator for no less
than 15 minutes.

17. Using the propeller flange bushing tool (ST-115), press new bushings into
the holes.

72-60-06e4 Crankshaft (Straightening Flange)

1. Measure the crankshaft flange run-out on the face of the flange between the
bushing and the periphery of the chamfer using a dial indicator.

2. Replace the crankshaft if the flange run-out exceeds 0.018 in. total indicator
run-out (TIR). If the flange run-out is less than 0.018 in. TIR, the flange may
be straightened.

3. Refer to Figure 72-60-06-17.

4. Remove the propeller flange bushings using the propeller flange bushing tool
(ST-115).

Figure 72-60-06-17. Limits for Straightening Bent Flanges

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

5. Make the front face of the flange perpendicular to the shaft centerline by
grinding.

6. Measure the thickness of the flange at Dimension A (Figure 72-60-06-17).

Replace the shaft if the minimum thickness measurement after grinding is
less than 0.420 in.

Caution
Exercise extreme care during any straightening operation to avoid
damage to the nitrided surfaces of the crankshaft. The nitrided surfaces
are “glass hard” and extend from the front face of the slinger to the
crankshaft gear mounting surface. If the shaft is bent, dropped, or
handled carelessly, the nitrided surfaces will crack and the shaft must be
replaced.

7. Have the crankshaft inspected by a certified operator using magnetic particle

testing, paying particular attention to the bearing surfaces and to the fillet
areas at the base of the flange.

8. Install the flange bushings using the propeller flange bushing tool (ST-115).

9. Apply a 0.0005 in. cadmium plating to the ground surfaces of the crankshaft
flange and along the crankshaft as shown in Figure 72-60-06-16.

72-60-06e5 Crankshaft (Counterweight Bushing Replacement)

Dynamic counterweights are installed on engine crankshafts to eliminate
vibrations caused by torsional frequency changes that occur at different engine
speeds and operating conditions. Each counterweight is mounted on the
crankshaft with two steel rollers that allow the counterweight to move as required
for maintaining crankshaft balance. Both the counterweight supporting lug of the
crankshaft and the counterweight itself contain hardened steel bushings that are
ground to a very smooth and annular finish. If any of these bushings become
damaged or worn out-of-round, the counterweight will become ineffective and
will cause vibrations that will lead to severe engine damage.

Refer to Figure 72-60-06-18.

Caution
Failure to replace crankshaft counterweight bushings at overhaul could
cause failure of the counterweights, the crankshaft and, ultimately, the
engine.

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Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

Caution
Never use a drift to remove or install crankshaft counterweight lug
bushings.

Note: Reassemble all counterweights and their related parts in the same
location they occupied on the crankshaft before disassembly. For
example, the washers used with the counterweights are selectively fitted
to the washer seats in that counterweight during manufacture.

Counterweight Lug Bushing Removal

Refer to Figure 72-60-06-18.

Figure 72-60-06-18. Removal of the Crankshaft Counterweight Lug Bushing

1. Thread the bolt of the counterweight bushing puller (P/N 64872) through the
puller plate.

2. Insert the counterweight bushing puller bolt through the counterweight lug
bushing in the crankshaft.

3. Position the recess in the puller plate next to the crankshaft.

4. Install the small puller bushing over the end of the bolt.

5. Slowly tighten the puller bolt to extract the bushing from the crankshaft
counterweight lug and into the puller plate recess.

6. Remove the puller.

7. Using an inside micrometer, measure the ID of the counterweight bushing

hole in the crankshaft counterweight lug.

8. Select the appropriate reamer according to Table 72-60-06B.

Note: Reaming is not required if the hole ID is 0.9369 in. to 0.9377 in.

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Table 72-60-06B. Counterweight Bushing Size Chart

Hose Size (in.) Reamer No.
Std. 0.9369/0.9377 None
O-size 0.9420/0.9425 P/N 64894
O-size 0.9445/0.9450 ST-210
O-size 0.9470/0.9475 P/N 64875
O-size 0.9495/0.9500 ST-211
O-size 0.9520/0.9525 P/N 64876

Caution
Do not machine the new counterweight bushing. The ID of these
bushings is finished at the factory and no further machining of the
bushing is necessary. Exercise caution when installing the bushing to
ensure that this finished ID is not damaged.

Caution
Do not damage the interior surface of the counterweight bushing.

Counterweight Lug Bushing Reaming

Refer to Figure 72-60-06-19.

Figure 72-60-06-19. Crankshaft Counterweight Lug Bushing Reamer (ST-280)

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Note: If reaming of the counterweight lug bushing hole in the crankshaft is not
required, proceed to Counterweight Lug Bushing Replacement.

1. Assemble the crankshaft counterweight reaming fixture (ST-280) over the

crankshaft lug.

2. Select the two openings in the fixture to line up with the bushing holes.

3. Install the plugs (ST-280-3, ST-280-7, ST-280-8, ST-280-9, ST-280-10, or

ST-280-11) to line up the holes in the fixture with the holes in the crankshaft
lugs.

4. Secure the crankshaft in the fixture by tightening the setscrews.

5. Assemble the reamer to a suitable universal joint drive. Hand ream the hole
in the crankshaft lug to the proper size.

6. Remove the reaming fixture and realign it to ream the other hole. Repeat
steps 3 through 5.

7. Remove the reaming fixture.

Counterweight Lug Bushing Replacement

1. Assemble the puller (P/N 64872) to the crankshaft.

2. Place the new crankshaft counterweight lug bushing on the puller bolt
between the crankshaft counterweight lug and the large puller bushing.

Caution
Do not damage the interior surface of the counterweight bushing.

3. Tighten the puller nut to insert the new bushing into the crankshaft.

4. Remove the puller.

5. Place the crankshaft in V-blocks on a surface plate.

6. Install wedge blocks (ST-212) in the bushing.

7. Compare the parallelism of the wedge blocks with the main journals. The
bushing must be parallel to within 0.002 in.

72-60-06e6 Counterweights (Inspection, Replacement, and Blancing)

Counterweight Bushing Replacement

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1. Visually inspect the bushings located in the counterweight for wear or out-
of-round ID.

2. Using the bore gage (ST-73), measure the diameter of the bushing. The
diameter should measure 0.7485 in. and 0.7505 in. Out-of-round should not
exceed 0.0005 in.

3. Replace bushings that exceed these measurements.

4. Place the special driver (ST-92) in an arbor press.

5. Position the counterweight so that it lays flat against the lower surface and is
square with the arbor press spindle.

6. Press both bushings out of one side of the counterweight.

7. Turn the counterweight over and align it as in step 5.

8. Press out the remaining two bushings.

9. Remove the counterweight from the arbor press and visually examine the
bore ID. It must be smooth and free of any scratches, tool marks, galling, or
other surface damage.

10. Discard the counterweight if the ID of any of the counterweight bushing

holes exhibits any damage.

11. Measure the ID of the counterweight bushing hole using an ID micrometer.

Bushing bores will fall between 0.9369 to 0.9377 in. or between 0.9384 to
0.9392 in. Discard the counterweight if the bores do not fall within these
bore ranges.

Note: Counterweight bushing bore IDs having the larger diameter will be
marked with a “B” near each bore. When ordering counterweight
bushings, if a “B” is marked near the bore, order the bushing with a “-B”
suffix on the part number.

12. Have the counterweights subjected to magnetic particle testing by a certified

operator. Replace the counterweight if testing reveals any indication of
cracks.

Caution
Do not, under any circumstances, attempt to enlarge the bushing bore in
a counterweight. Eventual engine damage will result from any operation
that reduces the snap ring groove depth in the counterweight bushing
bores.

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Counterweight Bushing Installation

Caution
The spacers provided with the counterweight fixture (ST-93) control the
depth to which the bushings are driven into the counterweight. The
bushings must be flush to 0.002 in. to prevent them from protruding into
the slot of the counterweight.

1. Measure the centerline to centerline distance of the bushing bores in the

counterweight.

2. Select the two holes in the counterweight fixture (ST-93) that correspond
with this measured distance.

3. Install the two locating pins (ST-93-2) in the selected holes. Refer to Figure
72-60-06-20.

Figure 72-60-06-20. Installing Counterweight Bushing

Using Fixture ST-93 and Driver ST-92

4. Install the spacer (ST-93-3 or ST-93-5) in the counterweight.

5. Position the counterweight and spacer on the fixture (ST-93) with the pins
(ST-93-2) located in the bushing bores.

6. Install the bushing driver (ST-92) in an arbor press.

7. Position the counterweight fixture so that it holds the counterweight and

spacer square with the arbor press spindle.

8. Press the new bushings into place on the upper side of the counterweight.

9. Turn the counterweight over.

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10. Install bushings in the same manner in the opposite side of the
counterweight.
11. Secure the bushing ID grinding fixture (P/N 64878) on the faceplate of a
suitable internal grinding machine fitted with a ¾ x 1 x ¼ in. grinding wheel
(P/N 3A-100-N6-V22 from Bay State Abrasive Division, Dresser Industries,
Inc., 12 Union St., Westboro, MA, 01581).

12. Ensure that the 1-1/8 in. diameter construction hole in the center of the
fixture is concentric with the center of the grinding machine faceplate.

Caution
Concentricity must be held to within ± 0.0005 in. TIR.

13. Install spacer on the alignment bar of the fixture. Refer to Figure
72-60-06-21.

Figure 72-60-06-21. Identification of Dimensions “A” and “B”

14. Tighten the three ¼-20 socket head screws.

15. Align the fixture through the unfinished bushing using a locating pin (P/N
64872-2).

Note: This locating pin is offset to accommodate the two different centerline to
centerline bushing bore distances found on counterweights.

16. Install and rotate the pin (P/N 64878-2) to the position required to place one
set of bushings on the centerline of the fixture.

17. Tighten the 10-32 socket head screw to lock the locating pin in this position
and secure the locating clamp (P/N 64878-23).

18. Ensure that the counterweight and fixture mating surfaces are clean.

19. Install the counterweight on the fixture.

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20. Secure the counterweight against the spacer by tightening the knurled head
screw.

Note: If the threaded end of the screw attempts to enter the slot in the
counterweight, release the screw and install a metal block
(P/N 64878-21) on the end of the screw.

21. Adjust the fiber block of the hold-down clamp over the center of the
counterweight.

22. Tighten the socket head screw to secure the counterweight to the fixture.

23. Grind the ID of both bushings to a 0.7485 to 0.7505 in. ID with the surface
finish of the finished bushing being 15 micro-in.

24. Remove the counterweight from the fixture and remove the locating pin (P/N
64872-2).

25. Install the locating pin (P/N 64878-6) in the opposite hole.

26. Rotate the pin to align the unground bushings with the centerline of the
fixture.

27. Secure the pin and counterweight as described in steps 16 through 22.

28. Grind the remaining bushing as described in steps 23 and 24.

Counterweight Bushing Inspection

1. Subject the newly ground counterweight bushings to magnetic particle

inspection by a certified operator to determine if there are any grinding
cracks present in the finished bushing.

2. Replace any bushings that are found to be cracked.

3. Inspect the bushing bores for correct location using Set-Master and gage
fixture (ST-94). Refer to Figure 72-60-06-22.

4. Refer to Figure 72-60-06-22. Install the relieved locating pin (ST-94-2) in the
center hole of the Set-Master with the locating diameters in the vertical
position.

5. Install the solid locating pin (ST-94-3) in the outside hole having the same
centerline-to-centerline distance as the counterweight bushing bores.

Note: The ST-94-2 pin can remain permanently installed in the center hole with
pin ST-94-3 being moved, as required, to adapt to the counterweight
being inspected.

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Figure 72-60-06-22. Depth Gage Adjusted with Set-Master Preparatory to

Checking Line Position of Counterweight Bushings

6. If the pins do not fit into the newly ground bushing, the bores are incorrectly
located. Replace the bushings.

7. Measure the distance from the center of the bushing bore to the flat edge of
the counterweight.

a. Place the Set-Master over the locating pins of the fixture.

b. Preload the depth gage approximately 0.010 in.

c. Rest the plunger on the step of the Set-Master identified as the “A”
dimension. Note the measurement shown on the dial indicator.

d. Remove the Set-Master and install the counterweight over the pins.

e. Refer to Figure 72-60-06-23. Set the depth indicator through the fixture
and onto the counterweight. There should be no more than a ± 0.004 in.
difference between this measurement and the measurement obtained with
the Set-Master.

8. Install the spacer (ST-91-7, ST-91-8, ST-91-9, ST-91-10, ST-91-11, ST-91-

12, ST-91-13, or ST-91-14) and the counterweight in the gage fixture
(ST-91).

9. Press the counterweight squarely against the spacer.

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Figure 72-60-06-23. Checking Centerline Position of Counterweight

Using Gage Fixture ST-94

10. Secure the counterweight firmly against the locating surface of the fixture by
tightening the knurled screw.

11. Refer to Figure 72-60-06-24. Install the gaging arbors (ST-91-3) through
each of the finished bushings.

Figure 72-60-06-24. Checking Parallelism and Squareness of Counterweight Bushings

with Gage Fixture ST-91 (Vertical Position)

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12. Refer to Figure 72-60-06-25. Place the fixture on a flat and clean surface
plate and indicate both ends of each arbor.

13. Refer to Figure 72-60-06-25. Turn the fixture over to rest on its adjacent side
and again indicate both ends of its gaging arbors. The difference in
measurements from one end of the gaging arbor to the other must not exceed
0.003 in. per inch in any instance.

Figure 72-60-06-25. Checking Parallelism and Squareness of Counterweight Bushings

with Gage Fixture ST-91 (Horizontal Position)

Counterweight Balance Procedure

The center of gravity of the counterweight is located at the center of the drilled
hole located between the bushing bores. The balance of the counterweight in
relation to its center of gravity is very important and may have changed when the
new bushings were installed. Check the balance of the counterweights.

1. Install the counterweight on the balancing arbor (ST-96-1 or ST-96-2).

2. Refer to Figure 72-60-06-26. Place the arbor on a pair of balancing ways so

that each blade of the way engages the arbor at a point not more than 1-1/2
in. from each end.

Note: The center of the arbor is tapered to compensate for slight variations in
the diameter of the hole. The first 1-1/2 in. of each end of the arbor is
carefully ground to ensure concentric diameters.

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Figure 72-60-06-26. Counterweight Mounted on ST-96 Arbor for Balancing

3. Refer to Figure 72-60-06-26. If the counterweight is in perfect balance, it

will remain in any position it is placed.

Figure 72-60-06-27. Counterweight Balanced by Weight ST-95 Placed

One Inch from Center

4. Refer to Figure 72-60-06-27. If the counterweight has a tendency to move,

place it not more than 1 in. from the center of the arbor. If the counterweight
can be brought into balance with the addition of this weight, the balance is
satisfactory.

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Figure 72-60-06-28. Location of Areas on Counterweight for Grinding

5. Refer to Figure 72-60-06-28. If the counterweight cannot be brought into

balance by the addition of the ST-95 weight, grind the counterweight in the
areas indicated.

6. Weigh the counterweight following grinding.

72-60-06e7 Connecting Rod Bushings

Measure the ID of the connecting rod bushing using an inside micrometer. If the
connecting rod bushing is worn beyond service limits, remove and replace it as
directed below.

Connecting Rod Bushing Removal

1. Loosely clamp the connecting rod onto the connecting rod bushing
replacement block (P/N 64597).

2. Align the small bushing in the connecting rod with the hole marked “Remove
Bushing.”

3. Drive the bushing out of the rod using the connecting rod bushing removal
drift (P/N 64535).

Connecting Rod Bushing Replacement

1. Loosen the clamp holding the connecting rod to the block.

2. Move the connecting rod to the “Install and Burnish” position.

3. Clamp the connecting rod securely into place.

4. Align the split in the bushing so that it is located toward the piston end of the
rod and is 45 degrees off the centerline of the connecting rod.

5. Drive the new bushing into place using the replacement drift (P/N 64536).

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6. Install the connecting rod into a suitable arbor press and connecting rod
bushing burnisher (P/N 64580).

7. Burnish the ID of the bushing by passing the burnisher completely through

the bushing.

8. Remove the connecting rod from the holding block.

9. Finish bore the bushing to the diameter shown in the Table of Limits.

Note: Measure the bushing ID with the finish ID gage (P/N 64767).

10. Check the alignment of the hole in the bushing with the connecting rod
parallelism and squareness gage (P/N 64530). Refer to “Connecting Rods
(Squareness Check)” and “Connecting Rods (Parallelism Check).” If the
finished assembly does not meet the requirements in the Table of Limits,
discard and replace the entire connecting rod assembly.

72-60-06e8 Crankshaft and Gear Assembly

Refer to Figure 72-60-06-29.

Figure 72-60-06-29. Crankshaft and Gear Assembly

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Caution
Use of damaged, worn, or broken parts may result in engine failure.

Caution
Before making any repairs to the crankshaft, inspect the counterbored
gear mounting face of the crankshaft for galling or fretting. If galling or
fretting exists, replace the crankshaft.

1. Examine the threads in the gear retaining bolt hole of the crankshaft.

Caution
Exercise extreme care when cleaning threads with a tap to avoid
damaging the threads. Make certain that you have selected the correctly
sized tap. If the incorrect tap is used, the hole may be made too large to
engage the threads on the bolt properly.

2. Select an undamaged standard threading tap from Table 72-60-06C.

Table 72-60-06C. Tap Chart

Thread Size Tap Size

5/16 in. 0.3125-24NF3 (P.D. 0.2854/0.2878 in.)

½ in. 0.500-20NF3 (P.D. 0.4675/0.4701 in.)

3. Insert and carefully withdraw the selected tap to clean the threads.

4. Thread a gear retaining bolt (15) to the bottom of the hole.

5. Compare the exposed length of the bolt with the thickness of the gear (13)
and lockplate (14).

6. Inspect the dowel in the end of the crankshaft for smoothness and for nicks
or deformities.

7. Inspect the dowel for out-of-roundness. Replace the dowel if it is out-of-

round.

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Figure 72-60-06-30. Section Through Figure 72-60-06-31. Section Through

End of Crankshaft Showing Driven Height End of Crankshaft Showing Driven Height
of STD-1065 Dowel and Dowel Details of STD-2078 Dowel and Dowel Details

Caution
Do not damage the crankshaft hole when installing the dowel.

8. If the dowel condition is acceptable, install it as shown in Figure

72-60-06-30 or 72-60-06-31.

9. If the dowel is to be replaced, use the following steps.

a. Drill a 1/8 in. hole through the center of the dowel.

b. Fill the hole with oil and insert a piece of 1/8 in. drill rod into the hole.

c. Strike the end of the drill rod a sharp blow with a hammer. The hydraulic
pressure of the oil will force the dowel from the crankshaft.

10. Check the pilot diameter of the counterbore on the end of the crankshaft for
size and evidence of damage. If the diameter exceeds 2.1262 in. when
measured at any location, repair the crankshaft using the following steps.

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a. Refer to Figure 72-60-06-32. Machine the pilot diameter in the end of the
crankshaft to 2.129/2.130 in.

b. Check that the surface and the pilot diameter are true within 0.001 in.
TIR.

c. Cut the 0.09 in. deep x 0.06 radius in. undercut as shown.

Caution
Do not attempt to reuse a crankshaft that has previously been machined
oversized.

Figure 72-60-06-32. Details for Repairing Pilot Diameter of Crankshaft

Figure 72-60-06-33. Minimum Dimension of Crankshaft

d. Chrome or nickel plate the surface of the pilot diameter with a firmly
bonded deposit that is free of pin holes, blisters, or any other
imperfections that could impair the function of the parts.

e. Stress relieve the shaft after plating by baking at 390° to 410°F (199° to
210°C) for 3 to 5 hours.

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f. Grind the plated pilot diameter surface to 2.125 to 2.126 in.

g. Verify that the pilot hole axis is parallel to, and the facing surface is
perpendicular to, the rear main journal to within 0.001 in. total indicator
reading.

h. Inspect the crankshaft counterbored gear mounting face for damage.

i. If the mounting face requires repair other than for fretting or galling,
measure the crankshaft as shown in Figure 72-60-06-32.

j. If the crankshaft measures more than the minimum dimension specified

in Figure 72-60-06-33, rework the surface to the dimensions shown. (Do
not replate the surface.) The surface must be true to within 0.001 in. TIR
to the rear main bearing, and the surface finish must be held to 45 to 50
micro-in.

k. Chamfer the edge of the pilot diameter 45° x 0.03 in.

11. Inspect the dowel hole in the crankshaft. If out-of-round, replace the dowel
as in steps 9a. through 9c. above. If oversize, ream as required for steps 10a.
through 10j. above (refer to Table 72-60-06D).

Table 72-60-06D. Dowels and Dowel Holes

Size Diameter of
Code Diameter “A” Hole
on (Figs. 72-60-06-32 & 33) in Crankshaft
Dowel P/N Dowel (in.) (in.)

STD-1065 None 0.3095/0.3100 0.3085/0.3095

STD-1065-P02 P02 0.3115/0.3120 0.3105/0.3115

STD-1065-P05 P05 0.3145/0.3150 0.3135/0.3145

STD-1065-P10 P10 0.3195/0.3200 0.3185/0.3195

STD-1065-P15 P15 0.3245/0.3250 0.3235/0.3245

72-60-06e9 Starter Ring Gear

The following procedure is for the replacement of worn or damaged starter ring
gears without replacement of the support assembly.

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1. Check the propeller bolt holes in the support assembly. Replace the entire
starter ring gear and support assembly if any are worn out-of-round.

2. If the propeller bolt holes are satisfactory, grind through the ring gear,
leaving only a thin ring of ring gear metal. Do not grind into the support
assembly.

3. Place the assembly on a flat metal surface and break the thin metal ring
remaining from the grinding operation. The ring gear springs open and is
easily removed.

4. Examine the ring gear support face. Do not reuse the ring gear support if it is
damaged.

5. Place the support on a flat surface with the generator belt groove upward.
Refer to Figure 72-60-06-34.

Figure 72-60-06-34. Section through Ring Gear Support

6. If a new ring gear is needed, use P/N 72566, 12/14 pitch. Use P/N LW-16471
for a new starter ring gear support assembly.

7. Heat the ring gear in an oven or by local application of heat with a torch. The
temperature should be approximately 450°F (232°C).

8. Assemble the heated gear, with the tooth chamfer upward, on the ring gear
support.

9. Using a 0.0015 in. feeler gage, check for clearance between the ring gear and
the support, around the circumference. Clearance at any location is an
indication of incomplete assembly or warping and must be corrected.

10. The gear will shrink to the support as it cools.

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11. Find the timing mark on the ring gear support and extend it across the ring
gear. Acid etch the timing mark extension on the ring gear.

12. Mark the newly overhauled ring gear assembly by adding the suffix “-85” to
the part number by vibro-peening or with the light impression stamp.

72-60-06f Reassembly
Refer to Figure 72-60-06-35.

Figure 72-60-06-35. Crankshaft Plug Location

72-60-06f1 Plug

1. Replace the plug located at the rear of the bore in the front of the crankshaft
if it was removed during overhaul. (Refer to Figure 72-60-06-35.)

2. Slide the plug sideways into the cavity inside the crankshaft past the
crankshaft propeller oil tube.

3. Tamp the plug into position.

72-60-06f2 Propeller Flange Bushings

Refer to Figure 72-60-06-36 and Table 72-60-06E.

Install new propeller flange bushings using the crankshaft flange bushing
replacement tool (ST-115) as required.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-06

Fgure 72-60-06-36. Type 2 Propeller Flange Bushing Location

Table 72-60-06E. Propeller Flange Bushing Location

Bushing Location

Model A B C D E F
(Indexing Bushing)

-A1A6 72155-S 75656-S 75656-S 72155-S 75656-S 79024-S

-A3A6 75656-S 75656-S 72155-S 75656-S 75656-S 75657-S
-A1B6 72155-S 75656-S 75656-S 72155-S 75656-S 79024-S
-A3B6 75656-S 75656-S 72155-S 75656-S 75656-S 75657-S
72-60-06f3 Crankshaft Gear
1. Clean the threads with compressed air and check the condition of the threads
in the end of the crankshaft by screwing a new attaching bolt in and back out
by hand. Refer to Figure 72-60-06-37.

Caution
No field repair of crankshaft gear attaching threads is permitted.

2. Check the condition and diameter of the dowel.

3. Assemble the crankshaft gear to the crankshaft. Refer to Figure 72-60-06-37.

a. Examine the slot and teeth of the gear.

b. Examine the dowel and pilot hole of the flange.

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Section 72-60-06 IO-390-A Series Maintenance and Overhaul Manual

a. Use a new lockplate.

b. Use a new bolt ensuring that the bolt threads are clean, dry, and free of
all foreign substances.

c. Lightly lubricate the threads of the bolt using a small amount of Loctite
Food Grade Anti-Seize (P/N 1167237).

d. Wipe the threads leaving the Loctite retained between the threads only.

e. Torque bolt to 125 in.-lb.

f. With a hammer and brass drift, tap lightly around the pilot flange of the
gear to ensure that the gear is seated on the crankshaft.

g. As a check, attempt to insert a 0.001 in. feeler gage between the gear and
the crankshaft at each scallop. The feeler gage must not fit at any
location.

h. Torque bolt to 204 in.-lb.

i. Measure the clearance between the OD of the gear flange and the pilot
ID of the crankshaft. There should not be more than .0005 in. clearance
at any point.

Figure 72-60-06-37. Rear End View of Crankshaft Showing Associated Parts

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

72-60-06f4 Counterweight Assembly

Caution
Ensure that each washer, and all parts, matches the seat it occupied
before disassembly using the identifying marks made on each part of the
counterweight assembly.

Note: Washers are installed with the chamfered side in toward the roller and
the circlip with the sharp side toward the outside and the gap in position.
Refer to Figures 72-60-06-38 and 72-60-06-39.

1. Insert a washer into the retaining ring on one side of the counterweight.

2. Insert the retaining ring on one side of the counterweight.

3. Place the counterweight on its matching ear on the crankshaft.

4. Insert the matching roller.

5. Install the washer and retaining ring on the second side of the counterweight
repeating steps 3 and 4 above.

6. Measure the gap between the end of the retaining ring on both sides of the
counterweight.

Figure 72-60-06-38. Assembly of Washer and Circlip in Counterweight

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Figure 72-60-06-39. Location of Gap When Installing Retaining Rings

a. Insert one end of the counterweight retaining ring gap gage (P/N 64892)
between the ends of the retaining ring, ensuring that the gage is resting
on the bottom of the groove.

b. Rock the gage back and forth to see if the gage clears the inside edge of
the top of the retaining ring. If the gage does not pass freely between the
ends and under the top of the ring, the ring is not seated properly.

7. Reseat the ring and repeat steps 6a. and 6b., ensuring that all rings are
correctly seated using the appropriate gage (P/N 64892).

8. If the rings do not seat firmly, examine the counterweight for burrs in the
snap ring groove.

a. Inspect the mating parts.

b. Lightly stone away any burrs found in the snap ring groove.

c. Insert a new snap ring.

72-60-06f5 Connecting Rods

Note: Connecting rods are marked at manufacture with a part number followed
by a letter (“A” through “E”) designating weight groups. Replacement
rods must be of the same weight group. Individual rods may also be
replaced with a service rod bearing the letter “S.”

1. Install two new connecting rod bolts in the connecting rod cap.

2. Install new bearing rod inserts in the connecting rod and connecting rod cap.

3. Align the tang of each bearing insert with the locating slot in the cap and in
the connecting rod.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-06

1. Thread a nut onto each connecting rod bolt and tighten the nuts so that the
rod and cap mating surfaces meet.

2. Measure the ID of the bearing.

3. Compare the measurements with those taken previously for clearance of the
diameter of the crankpin journals (refer to section 72-60-06d) and with the
clearances in the Table of Limits.

4. Place the crankshaft on a suitable support on the bench so that all crankpins
are accessible for the installation of the connecting rods.

5. Disassemble the connecting rods.

Caution
The IO-390-A1A6 engine utilizes high crush bearings that require a light
coating of Fel-Pro C5A anti-seize compound.

6. Thoroughly coat the inside surface of the inserts and the crankpin journals
with a mixture of 15% STP and 85% 50-weight aviation oil.

7. Assemble the rods on their respective crankpins so that the numbers stamped
on the caps and rods are oriented down (toward the sump).

8. Ensure that the connecting rod bolt and nut is free of dirt and debris and that
the threads are not damaged.

9. Apply a light coat of Loctite Food Grade Anti-Seize Lubricant P/N 1167237
to the bottom two or three threads of the bolt only. With a clean, lint-free
cloth, wipe away any excess.

10. Tighten the stretch bolt and nut, checking the length with a stretch bolt gage
(P/N 64945) until the stretch bolt measures 2.255 in. If 35 ft.-lb. of torque
fails to give minimum stretch (2.255 in. length) additional torque can be
applied until proper stretched length results. If 35 ft.-lb. results in an over-
stretched bolt (greater than 2.256 in. length) it must be replaced. Considering
possible variables in the joint that could increase the torque required to
achieve specified stretch, including thread irregularities and possible dirt, a
maximum torque of 55 ft.-lb. is hereby recommended for assembling
connecting rods with stretch bolts. The recommended range of torque for
assembling connecting rods with stretch bolts is the following:

Initial Torque: 35 ft.-lb.

Maximum Torque: 55 ft.-lb.

Page 121, Section 72-60 Revised October 2010

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

Caution

If proper stretched length (2.255/2.256 inches) is not achieved within

these values, the bolt must be discarded and replaced.

Caution

The connecting rod bolt cannot be tightened correctly if the nut is

installed upside down. The raised edge, or lip on the one face of the nut
must be on the free end of the bolt; the flat face must be in contact with
the rod. Refer to Figure 72-60-06-40. Any time the connecting rod bolt
and nut is removed from the engine, both parts must be replaced
regardless of apparent condition.

Figure 72-60-06-40. Connecting Rod Bolt Nut

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

72-60-06f6 Camshaft

1. Assemble the tachometer shaft centering spacer.

2. Install the pin and tachometer shaft.

3. Secure with the retaining ring.

72-60-06f7 Crankcase

1. Place both crankcase halves on a suitable stand that allows the rods to pass
freely through the crankcase with the interior of each half of the crankcase
facing upward.

2. Place new bearing inserts in the center and rear main bearings of both
crankcase halves.
Note: The tang of each insert must fit into the recess in the crankcase.

3. Temporarily position the front main bearing in place in the left crankcase
half. Ensure that the bearing is properly seated on the two dowels.

Note: The front main bearing, unlike the center and rear bearings, splits on the
horizontal centerline of the engine.

4. Use a pencil to mark both lines of intersection between the crankcase parting
flanges and the bearing on the assembled bearing.

5. Use a pencil to mark a vertical reference on each bearing and the crankcase,
at any convenient point along the line of intersection, to locate the bearing
radial and axial planes.

Note: These marks are necessary to ensure proper seating of the bearing halves
on the two locating dowels when the crankshaft is placed into position in
the crankcase.

72-60-06f8 Propeller Governor Drive

The propeller governor drive is located on the lower right of the accessory
housing. Refer to Figure 72-60-06-5.

1. Lubricate the propeller governor drive shaft gear with a mixture of 15% STP
and 85% aviation-grade oil.

2. Insert the propeller governor drive shaft gear (10) into the adapter (13).

3. Place a new accessory driven gear washer (11) over the drive end of the shaft
and secure shaft in place with a 13/16 inch diameter external retaining ring
(14).

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Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

4. Using a new gasket, attach the adapter to the lower right side of the accessory
housing with four 5/16-18 plain nuts, plain washers and lockwashers.
5. Place the governor driven gear in the drive housing at the front left of the
crankcase.
6. Attach cover (16) on the exposed end of the drive as protection against dirt
and foreign matter.
7. Install elbow fittings (8, 9) in the propeller governor line boss at the front of
the engine and at the rear of the engine in the propeller governor drive
housing. Use Loctite 564 and torque elbow fitting (8) to 78 in.-lbs., then
tighten to position. Install “O” ring on elbow fitting (9) and using Food
Grade Anti-Seize torque the elbow fitting to 200 in.-lbs.
8. Assemble the propeller governor oil line (1) around the crankcase and oil
sump. Secure the propeller governor oil line to the crankcase and sump as
shown in Figure 72-60-06-5. Do not allow the propeller governor oil line to
touch any engine component.
9. Tighten the propeller governor oil line to the elbow fittings (8, 9).
72-60-06f9 Crankcase Assembly
1. Assemble the idler gear shaft to the rear of the crankshaft as follows:
a. Insert the pilot of the shaft into the hole in the crankcase.
b. Turn the shaft until the holes of the pilot flange align with the drilled
holes in the mounting pad of the crankcase.
c. Place a lockplate over the flange.
d. Secure with the fastenings.
2. Place the left crankcase half on a suitable support on the bench with the
cylinder pads down.

Caution
There must be approximately 6 in. of clearance between the crankcase
and the bench.
3. Lay the right crankcase half on the bench with the cylinder pads down.
4. Install a new oil seal ring at the base of each stud in the counterbored recess.
5. Remove the hydraulic tappet bodies from the cleaning basket and lubricate
them with a mixture of 15% prelubricant (STP or equivalent) and 85% SAE
50 mineral-base aviation-grade lube oil.
6. Replace the hydraulic tappet bodies to their positions prior to disassembly.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

Note: If a new or reconditioned camshaft is being used, only new tappet bodies
are recommended.

7. Prelubricate the camshaft lobes and bearings with a mixture of 15%

prelubricant (STP or equivalent) and 85% SAE-50 mineral base aviation
grade lube oil.

8. Lay the camshaft in position in the left crankcase half.

9. Refer to Figure 72-60-06-41. Loop a soft wire around an adjacent cylinder

pad stud to hold the camshaft in place when the crankshaft is turned over.

10. Prelubricate the main bearing journals of the crankshaft and the rear and
center main bearing inserts in the right crankcase half using a mixture of 15%
prelubricant (STP or equivalent) and 85% SAE 50 mineral-base aviation-
grade lube oil.

11. Liberally coat each bearing half.

12. Assemble the bearings on the crankshaft.

13. Rotate the bearing on the journal so that the three oil transfer holes will be
uppermost when the crankshaft is placed into the right crankcase half.

14. Lift the assembled crankshaft by the even-numbered connecting rods and
lower the crankshaft into the right crankcase half.

Figure 72-60-06-41. Illustrative Example of Camshaft Wired to Crankcase Half

15. Allow the odd-numbered rods to protrude through their respective cylinder
mounting pads.

August 2008 Page 125, Section 72-60

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

16. Use the reference marks made earlier to adjust the front main bearing so that
the halves are seated squarely on the locating dowels.

a. Refer to Figure 72-60-06-42. With the crankshaft located in the right

crankcase half, push the crankshaft forward as far as possible.

b. Measure the crankshaft slinger clearance using a feeler gage at Point

“B.” Clearance must measure 0.002 to 0.007 in.

c. If the clearance is less than 0.002 in., regrind the front face of the
crankshaft slinger an amount sufficient to achieve the clearance.

d. Push the crankshaft to the rear of the crankcase as much as possible.

e. Measure the clearance between the thrust surface of the crankshaft and
the crankcase using a feeler gage. Clearance must measure 0.009 to
0.026 in.

17. Prelubricate the main bearing inserts of the left crankcase half using a
mixture of 15% prelubricant (STP or equivalent) and 85% SAE 50
mineral-base aviation-grade lube oil.

18. Apply a film of non-hardening gasket material such as POB #4 Perfect Seal
sealing compound to the outside mating surfaces of each crankcase half.

Note: POB #4 Perfect Seal Compound is available from Perfect Seal,

Cincinnati, OH 45223, 513-542-8444.

Figure 72-60-06-42. Checking the Crankshaft End Clearance

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

Caution

Do not apply the gasket compound to any of the interior mating surfaces,
such as the bearing support webs.

Caution

Only Lycoming approved sealants are to be used in this application. Use

of any other non-approved sealant could result in a loss of clamping
force and/or torque, which will render the engine unairworthy.

19. Imbed two lengths of “00” silk thread in the gasket compound so that both
threads lie in the area between the bolt holes and the inside edge of the
crankcase half, making sure that the thread lengths do not touch or cross over
one another. Refer to Figure 72-60-06-43.

20. Press the thread firmly into the sealant.

Note: In some field service locations where “00,” silk thread is not readily
available, use steps 22 through 24 to apply sealant to the crankcase
halves.

21. Apply a very thin film of RTV-102 or Loctite-515 to only one half of the
crankcase so that it produces a wet appearance on the machined surface, as
shown in Figure 72-60-06-44.

Note: RTV-102 is available from General Electric Company, World

Headquarters, 187 Dambury Rd., Wilton, Ct. 06897. Loctite-515 is
available from Henkel Loctite Corp., 1001 Trout Brook Crossing, Rocky
Hill, CT 06067.

August 2008 Page 127, Section 72-60

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-06-43. Sealing Area for P.O.B. Sealant and “00” Silk Thread

Figure 72-60-06-44. Sealing Area for RTV-102 and Loctite 515

22. Wipe all excess sealant from the inner edges of the crankcase.

23. Ascertain that no sealant has come in contact with the bolt holes or with any
surface other than those shown above.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

24. Lift the right half of the crankcase and, keeping the halves parallel, lower the
right half of the crankcase over and onto the left half so that the studs align.

25. When the cases are aligned properly, tap the right half of the crankcase with
a rubber mallet to seat the crankcase firmly all around.

26. Install all crankcase fasteners.

27. Tighten the studs and bolts. Refer to Figure 72-60-06-45.

Figure 72-60-06-45. Crankcase Tightening Sequence

28. Refer to Figure 72-60-06-46. Assemble bolts over all the thru-studs on both
sides of the crankcase.

29. Refer to Figure 72-60-06-47. Assemble the torque hold down plate (ST-222)
at the cylinder pads over the bolts.

30. Attach the plates with washers and nuts.

31. Tighten the nuts only fingertight at this time.

32. Using the sequence shown in Figure 72-60-06-45, tighten the nuts to 300 in.-
lb.

33. Ensure that the plates remain parallel with the cylinder decks of the
crankcase and that the crankcase halves are pulled together evenly. Refer to
Figure 72-60-06-48.

August 2008 Page 129, Section 72-60

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

Figure 72-60-06-46. Right Side of Crankcase Showing Bolts Installed on Thru-Studs

Figure 72-60-06-47. Right Side of Crankcase Showing Plate Assembled Over Bolts

Figure 72-60-06-48. Right Side of Crankcase Showing Pressure Plate Utilized to Pull
Halves of Crankcase Together

Page 130, Section 72-60 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-06

34. Repeat the same tightening sequence, this time tightening the nuts to 600 in.-
lb.

35. Tighten the 3/8 in. nuts at the front main bearing to 300 in.-lb.

36. Using any sequence, tighten the remaining 1/4 in. nuts at the crankcase
parting face to 75 in.-lb..

72-60-06f10 Crankshaft Oil Seal Installation

Solid Ring Nose Seal.

1. Remove the spring from the inside of a new seal. Unhook the spring.

2. Apply a thin film of Lubriko M-6 grease (Master Lubricants Co.,

Philadelphia, PA) or equivalent on the sealing surface of the seal; around the
crankshaft at the sealing surface; and on the outer edge of the crankshaft
flange.

Note: If the crankshaft is not reinstalled in an engine, secure it in a vise or other

suitable support to prevent it from moving during assembly of the stretch
seal.

3. Place the seal over the edge of the crankshaft propeller flange with the rear
(open portion) of the seal towards the flange. Refer to Figure 72-60-06-49.

Figure 72-60-06-49. Crankshaft Propeller Flange

Showing the Installation of the Stretch Seal

August 2008 Page 131, Section 72-60

Section 72-60-06 IO-390-A Series Maintenance and Overhaul Manual

4. Slip a brass pin approximately 9/32 in. diameter x 3 in. long through the
crankshaft propeller flange bushing to retain both sides of the stretch seal.
Refer to Figure 72-60-06-49.
5. Install tool ST-383 under the seal and over the edge of the crankshaft
propeller flange as shown in Figure 72-60-06-49. With even pressure on the
handle, force the seal over the crankshaft propeller flange. Check to be
certain that no damage has occurred to the seal while it was being installed
over the flange.
6. Place the seal spring around the crankshaft, join the two ends together, and
hook the spring. The spring should be a continuous circle around the
crankshaft with no kinks or twists.
7. Work the spring into position in the groove (open portion) provided in the
rear side of the seal.
8. Using an appropriate solvent, remove the grease film from the crankshaft
flange; the outer surface of the seal and from the crankcase seal bore recess.
Apply a thin coat of adhesive (Dow Corning 737 Neutral Cure Sealant, or if
not available, Pliobond #20 may be used) to the outside diameter of the nose
seal and to the inner bore of the crankcase seal bore recess. Do not allow any
adhesive to come into contact with the crankshaft and especially the oil
return port. If any adhesive comes into contact with the crankshaft or oil
return port, use acetone to remove all traces of it.

9. Insert the seal in the crankcase bore. Apply pressure all around the nose seal
until it is seated firmly in the bore.

10. Allow 24 hours for the Dow 737 to cure. (If substituting the Dow sealant
with Pliobond #20, allow 15 minutes for the Pliobond to cure.)

Caution
Be sure no sealant gets on the ID of the seal or onto the crankshaft.
Split Nose Seal.
1. Assemble the split seal on the crankshaft with the front face of the seal
toward the crankshaft propeller flange. Note that the seal part number is
molded on the front of the seal.
2. Using an appropriate solvent, remove the grease from the crankshaft flange;
the outer surface of the seal and from the crankcase seal bore recess. Apply a
thin coat of adhesive (Dow Corning 737 Neutral Cure Sealant, or if not
available, Pliobond #20 may be used) to the outside diameter and the split of
the sel. Do not allow any adhesive to come into contact with the crankshaft
and especially the oil return port. If any adhesive comes into contact with the
crankshaft or oil return port, use acetone to remove all traces of it.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-06

3. Face the propeller end of the crankshaft and assemble the seal with the split
at 1:00 o’clock on standard rotation engines and at 11:00 o’clock on reverse
rotation engines. Apply a fresh coat of adhesive (Dow Corning 737 Neutral
Cure Sealant, or if not available, Pliobond #20 may be used)) to the inside
diameter of the crankcase then press the seal firmly against the seat in the
crankcase bore.

4. Allow 24 hours for the Dow 737 Neutral Cure Sealant to cure. (If
substituting the Dow Sealant with Pliobond #20, allow 15 minutes for the
Pliobond #20 to cure.)
72-60-06f11 Drive Belt and Ring Gear Support
1. Refer to Figure 72-60-06-34.

2. Place the drive belt in the pulley of the ring gear support.

3. Assemble the ring gear support over the propeller flange bushings.

Note: Make sure the bushing hole in the ring gear support marked with an “0”
is assembled over the flange bushing also identified with an “0” etched
on the crankshaft flange next to the bushing.

4. Locate the starter ring gear so that the “0” on the ring gear support aligns
with the tooth marked “0” on the crankshaft flange.
72-60-06f12 Crankshaft Idler Gears
1. Refer to Figure 72-60-06-50.

Figure 72-60-06-50. Idler Gear Diagram

Revised June 2009 Page 133, Section 72-60

Section 72-60-06 IO-390-A1A6 Maintenance and Overhaul Manual

2. Place the left crankshaft idler gear on the idler shaft located to the left and
between the camshaft and crankshaft gears.

Note: This dual gear is marked in three different places with timing marks in
the form of small etched circles. The smaller diameter gear is marked at
one place with the etched circles on two adjacent teeth, and the
crankshaft gear has small etched circles on single gear teeth at two
different locations. The single marked tooth on the idler gear must mesh
with the two marked teeth of the camshaft gear. The marked teeth of the
crankshaft gear must mesh with the marked teeth of the idler gear.

3. Install the right crankshaft idler gear in place on the idler shaft, ensuring that
the second marked tooth on the crankshaft gear meshes with the space
between the two marked teeth on the smaller gear surface of the idler gear.

Note: The magneto gears shown in Figure 72-60-06-50 are marked with a
circle on one tooth. This tooth must mesh between the two circles etched
on the adjacent teeth of the larger diameter gear of the crankshaft idler
gears.

Page 134, Section 72-60 August 2008

IO­390­A Series Maintenance and Overhaul Manual Section 72­60­07

72­60­07 OVERHAUL OF THE INDUCTION SYSTEM

72­60­07a General Information

The Lycoming IO­390­A1A Series engine has a bottom­mounted induction system
that includes a provision for icing protection and incorporates an air cleaner with
an air flow rated power of 1500 lb. air per hour. The cooling system in the IO­
390­A Series engine uses air built up on one side of the cylinder, then discharged
through the cylinder fins, to cool the engine.

Note: Aircraft that are operated from dusty airfields or in dust storm areas will
require additional air cleaner capacity.

72­60­07b Disassembly

72­60­07b1 Intake Pipes

Refer to Figure 72­60­07­1.

Figure 72­60­07­1. IO­390­A Series Induction System

2. Temporarily mark the intake pipes and their corresponding positions so that
they can be reassembled in the same position from which they were removed.

3. Loosen and remove the two capscrews that attach each intake pipe flange to
the intake cylinder port.

Revised June 2009 Page 135, Section 72­60

Section 72-60-07 IO-390-A1A6 Maintenance and Overhaul Manual

3. Pull the intake pipe from the induction housing.

4. Remove and discard the gaskets and o-rings.

72-60-07b2 Fuel Injector
Refer to Figure 72-60-07-1.

1. Disconnect lines and hoses.

2. Remove attaching bolts and hardware.

3. Remove the injector from the mounting pad on the inlet housing.
72-60-07b3 Induction Housing
Refer to Figure 72-60-07-1.

1. Remove the four attaching bolts attaching the induction housing.

2. Pull the induction housing from the oil sump.

72-60-07b4 Oil Sump Removal
1. Remove all attaching hardware that holds the sump to the crankcase.

2. Pull the sump from the crankcase.

3. Remove the gasket.

72-60-07c Cleaning and Inspection
Clean all parts of the induction system according to section 72-60-02b. Inspect
all parts of the induction system according to section 72-60-02c.

72-60-07d Reassembly
Intake Housing
1. Assemble the intake housing brackets to the underside of the intake housing.

2. Attach the intake housing brackets to the crankcase seam bolts.

Intake Pipes
1. Place new O-rings on the upper ends of each intake pipe.

2. Insert each intake pipe into the manifold in the inlet from which it was
removed.
Note: The intake pipes are manufactured to fit from a specific cylinder to a
specific corresponding inlet in the induction housing. Intake pipes are not
interchangeable and must be reassembled in the same location from
which each was removed.
3. Attach the flange and gasket to the cylinder using two bolts on each flange.

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IO-390-A Series Maintenance and Overhaul Manual Section 72-60-08

72-60-08 OVERHAUL OF THE FUEL SUPPLY AND FUEL INJECTION SYSTEM

72-60-08a General Information

The fuel delivery system for the IO-390-A Series engine utilizes a fuel pump that
delivers fuel to the RSA-5AD1 fuel injector. Fuel then travels from the fuel
injector to the fuel manifold or flow divider. A system of fuel injection lines to
injection nozzles at each cylinder provides fuel delivery to each cylinder.

Fuel lines are secured to the engine with support clamps, which dampen vibration
from the engine, the airframe, or from the impact of cooling air.

No attempt will be made in this manual to describe overhaul procedures for the
fuel pump. Replacement of the fuel pump is required at overhaul.

Lycoming recommends that the fuel injector be replaced at overhaul with a new
or serviceable fuel injector.

72-60-08b Disassembly
Refer to Figure 72-60-08-2.

72-60-08b1 Fuel Supply Lines

Caution
Do not attempt to repair a damaged fuel line. Replace any line that is
chafed, cracked, dented, or kinked; cracks can develop at the site of
bends or kinks.

4. Mark fuel lines for correct reinstallation.

5. Disconnect all the clamps and brackets that secure the fuel lines to the
engine.

6. Disconnect the fuel lines from the fuel manifold and from the fuel inlets at
the cylinders.

7. Disconnect any lines that supply fuel from the fuel pump to the fuel injector.

8. Check each line for damage or restrictions.

72-60-08b2 Fuel Injector

Refer to Section 72-60-02b2.

Revised June 2009 Page 137, Section 72-60

Section 72-60-08 IO-390-A1A6 Maintenance and Overhaul Manual

72-60-08c Cleaning

72-60-08c1 Fuel Injector Nozzle Assemblies

1. Remove the nozzles from the individual fuel lines using a wrench.

2. Insert a plug into the open end of each line to prevent dirt, dust, or other
contaminants from entering the fuel lines.

Note: Do not remove the shield and screen from the nozzle assembly.

Caution
Never use a sharp tool such as a wire or pin to clean out a nozzle.
Damage to the inlet and outlet fuel restrictors could result.

3. Submerge the nozzles in Hoppe’s Gun Cleaning Solvent #9 or equivalent and

allow to soak briefly.

4. Remove the nozzles from the solvent and dry with clean, compressed air.

5. If any gasoline or solvent has been spilled, clean it up in accordance with

federal, state, and local environmental regulations.

72-60-08d Inspection

1. Check the fuel manifold assembly for damage or signs of leakage.

2. Inspect all other lines and fittings for damage or signs of leakage. Refer to
Section 72-60-08f4.

Caution
Do not attempt to repair a damaged fuel line. Replace any line that is
cracked, dented, or kinked; cracks can develop at the site of bends or
kinks.

3. Reject any fuel lines that show evidence of bends or kinks.

72-60-08d1 Nozzle Assembly

1. Inspect the cleaned nozzles for any damage.

2. Reject any worn or damaged nozzles.

3. Upon reassembly, perform a flow check in accordance with Section 73-20-

01a8.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-08

72-60-08e Repair and Replacement

72-60-08e1 Fuel Injector
The fuel injector is not repairable. Replace with a serviceable part. Lycoming
recommends that the fuel injector be replaced when defective and at overhaul.
72-60-08e2 Fuel Pump

The fuel pump is not repairable. Replace with a serviceable part. Lycoming
recommends that the fuel injector be replaced when defective and at overhaul.
72-60-08f Reassembly
When the engine build-up has progressed to the point where the crankcase and
the accessory housing have been assembled and the cylinders installed, the fuel
delivery system may be assembled to the engine.

72-60-08f1 Fuel Injector

1. Place a new gasket on the fuel injector mounting pad.

2. Install the fuel injector on the gasket by attaching the mounting hardware.

72-60-08f2 Flow Divider

1. Mount the flow divider on the top of the engine so that its discharge nozzles
are in a horizontal plane on the top of the crankcase.

2. Attach the flow divider to the fuel manifold bracket.

72-60-08f3 Air Bleed Nozzles

Air bleed nozzles are installed in the upper side of the cylinder head. Install
nozzles so that the identification mark (a letter or figure located on the 0.500 in.
hex) is installed toward the bottom of the engine within approximately one hex
flat of 60 in.-lb.

72-60-08f4 Fuel Lines Inspection

As a means of minimizing the hazards of fuel line damage, the following
inspection of fuel lines and clamps is required.

1. The fuel lines to the nozzles are made from 1/8 inch tubing. A separate line
supplies fuel to the intake port of each cylinder. Check each line visually for
any evidence of physical damage and for stains caused by fuel leakage.

Note: When ordering fuel lines, the fuel lines are not pre-bent from the factory;
however fuel lines ends are pre-assembled. (Refer to Table 72-60-08A.)

August 2008 Page 139, Section 72-60

Section 72-60-08 IO-390-A1A6 Maintenance and Overhaul Manual

2. Remove any line that appears faulty. Do not attempt to repair any line that
leaks. Bent lines may be straightened; however, any line with an inside
radius less than 5/8 inch must be replaced. Do not reuse any line that is
dented; cracks can develop at the site of a dent. Also inspect solder joints at
end of lines for cracks. Replace cracked lines, they cannot be repaired.

3. Examine the location of the clamps that secure the lines to the engine and
compare them with Figure 72-60-08-2. If clamps are missing, replace fuel
line and install clamps as indicated. Also, examine the lines to ensure the
clamps securely support the line and for signs of chafing. Replace fuel lines
that show indications of chafing. See Table 72-60-08A for replacement lines.

4. Any cushioned clamp, where the cushion has deteriorated or is missing, must
be replaced with a new cushion clamp.

Note: If difficulty is experienced when installing clips on a cylinder fuel

injector line due to aircraft baffling, the clips may be installed in positions
that provide clearance. Do not permit fuel lines to contact engine or
airframe baffle hardware; maintain minimum clearance of 3/16 inch
between line and any engine surface.

Note: Refer to Figure 72-60-08-1 for minimum fuel line bending dimensions.

Figure 72-60-08-1. Minimum Fuel Line Bending Dimensions

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-08

Figure 72-60-08-2. IO-390-A1A6 Fuel Supply System

August 2008 Page 141, Section 72-60

Section 72-60-08 IO-390-A1A6 Maintenance and Overhaul Manual

Table 72-60-08A. Replacement Fuel Lines and Hardware

1 LW-12098-0-210 Tube Assembly, Fuel Injector Line

2 LW-12098-0-140 Tube Assembly, Fuel Injector Line
3 LW-16266-10-13 Clamp, 1/8 dia. for No. 10 screw
4 LW-16266-10-75 Clamp
5 73136 Bracket, 90°
6 STD-860 Screw, No. 10-32 x 5/8 long
7 STD-670 Nut, No. 10-32 self-locking

72-60-08f5 Fuel Line Installation

1. Consult Table 72-60-08A for the appropriate fuel line and clamp
replacements.

2. Install fuel line from the fuel pump to the fuel injector and from the fuel
injector to the flow divider.

3. Install fuel injector nozzle lines.

4. Form lines to fit as shown in Figures 72-60-08-1, 72-60-08-2, 72-60-08-3

and 72-60-08-4. Carefully bend the lines by hand insuring that no bend
radius is tighter than the specified .62 minimum radius. Kinking or flattening
of the line or any deformation that could cause flow restriction requires
replacement of the line.

5. Torque nut at both ends of tube to 25-50 in.-lbs.

6. Check all fittings and connections for leaks.

7. Install the fuel line clamps that secure the fuel lines to the engine.

Warning
All clamps listed in Table 72-60-08A must be installed and must be
installed in correct position as shown in Figure 72-60-08-2.

8. To check for leaks or restrictions, ground run the engine at 1800-2000 RPM
for approximately 3 minutes. During operation, check for smooth operation
and normal instrument readings. After shut down, inspect the engine for any
indication of leaks.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-09

72-60-09 TESTING AND RUN-IN FOLLOWING OVERHAUL

Once the newly overhauled engine is completely reassembled, Lycoming
recommends the engine be mounted on a test stand for a thorough evaluation and
run-in operation. This serves four purposes. First, it seats the piston rings and
burnishes any new parts that have been installed during overhaul. Second, it
gives the operator control over the first critical hours of operation so that the
function of the engine may be closely monitored and evaluated. Third, it provides
an opportunity to detect any malfunctions or oil leaks. Fourth, it enables
immediate repair of any conditions detected during testing before the engine is
reinstalled in the airframe.

Note: Although Lycoming recommends using a test stand for run-in of engines
after overhaul, it is possible to perform run-in operations with the engine
mounted in the airframe providing that a proper test club (not a flight
propeller) is used, that a cooling shroud equivalent to a test cell cooling
shroud is installed, and that all necessary calibrated gages (listed in 72-
60-09a2 below) be mounted independently of, and used instead of,
airframe gages. Test club propellers are available from any of the
following manufacturers:

Sensenich Wood Propeller Co. Arrowprop Company

2008 Wood Court P.O. Box 610
Plant City, FL 33563 Meeker, OK 74855
Phone: (813) 754-3711 Phone: (405) 279-3833
www.sensenichprop.com www.arrowprop.com
72-60-09a General

72-60-09a1 Test Stand

The test stand must be clean and free of any loose articles or items that could be
moved by the test club air blast.

72-60-09a2 Test Instruments and Equipment

The following instruments are required in addition to any other instruments
deemed necessary by the operator.

1. Temperature gage with a measuring range no less than 0° to 600°F (-18° to

315°C)

2. Counter tachometer

3. Fuel flow meter (optional)

4. Fuel pressure gage

August 2008 Page 143, Section 72-60

Section 72-60-09 IO-390-A Series Maintenance and Overhaul Manual

5. Manifold pressure gage

6. Oil temperature gage

7. Oil pressure gage

8. Cylinder head temperature gage

72-60-09a3 Test Stand Oil Supply Pressure

Engines equipped with an integral full-flow oil filter should be run-in with a
slave filter. The regular filter should be installed at the end of the run-in.

Note: If the engine is operated without the propeller governor installed, the
governor cover P/N 72378 and gasket P/N 72053 must be installed.

During run-in, it is important that oil temperatures be maintained within the

limits specified in Table 72-60-09A. Allow the engine to idle until the oil
temperature reaches 140° (60°C) before starting the run-in schedule.

72-60-09b Test Limits

Table 72-60-09A. IO-390-A Series Engine Run-In Test Limits

IO-390-A Series

Fuel Pressure (psi) at Inlet to Fuel 14-45

Injector

Maximum Oil Consumption (lb/hr) 0.006

Maximum Oil Consumption (qt/hr) 1.0

Operating Oil Pressure (psi): Normal 55-95

Operating Oil Pressure (psi): Idle 25

Max. pemissible 235°F
Oil Inlet Temperature: °F (°C)
(113°C)
Max. allowable 180°F
(82°C)
Maximum Cylinder Head Temperature, 475°F (246°C)
Bayonet Location: °F (°C)

Max. Continuous HP Speed (rpm) 2700

72-60-09c Run-in Procedure

1. Connect the oil and fuel control lines.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-09

2. Use MIL-L-6082 or SAE J1966 grade lubricating oil during run-in.

3. Use 100 or 100LL fuel.

4. Ensure that the test stand fuel system terminates in a float chamber that is
vented to the atmosphere and located at least 1 ft. below the entrance to the
fuel pump.

5. Ensure that the test stand fuel system maintains the fuel pressure to the
chamber at 2 to 5 psi.

6. Pre-oil the engine by forcing 35 psi of oil through one main gallery until the
oil flows from the opposite gallery with the front end of the gallery open.

7. Attach the instrument connections.

8. Connect the throttle and mixture control levers while ensuring that the cables
are free and do not bind. Ensure that the travel is sufficiently long to
completely open and close the throttle and to move the mixture control lever
from “FULL RICH” to “IDLE-CUT-OFF.”

9. Install the applicable cooling shroud, test club, and adapter. Ensure that the
test club will turn up rated rpm ± 50.

10. Prepare a log sheet to record the instrument readings during each speed in the
running schedule. Refer to Table 72-60-09B or 72-60-09C.

11. Make sure the magneto switch is in the “OFF” position.

12. Turn the engine over for a few revolutions to ensure that there are no
obstructions within the arc of the test club or within the engine itself.

Caution
If the engine does not turn freely, do not try to force it or make any
attempt to start it until the cause has been determined and the fault
corrected.

13. Start the engine using an electric boost fuel pump in the following order.

a. Place the mixture control selector in the “IDLE-CUT-OFF” position.

b. Turn the fuel valve to the “ON” position.

c. Set the throttle at the 1/10 open position.

d. Turn the magneto switch to the “START” position and engage the
starter.

e. Turn the combination magneto/starter switch to “START.”

August 2008 Page 145, Section 72-60

Section 72-60-09 IO-390-A1A6 Maintenance and Overhaul Manual

Table 72-60-09B. IO-390-A1A6 Ground Run-In Chart

Test Data

1. Avoid dusty locations and locations with Type Aircraft _____________________________

loose stones.
Registration Number _______________________
2. Head aircraft into the wind.
Aircraft Number ___________________________
3. All cowling should be in place with cowl
flaps open. Owner___________________________________

4. Accomplish ground run-in full flat pitch. Engine Serial Number ______________________

5. Never exceed 200°F (93°C) oil temperature. Date ____________________________________

6. Do not permit cylinder temperatures to exceed Operator _________________________________

400°F (187°C).

Ground Run
Time rpm MAP Temperature Pressure Temperature Fuel Flow
Amb
Oil Cyl. Oil Fuel Inj. Air Flow

10 1000
min

20 1200
min

20 1300
min

15 1500
min

10 1600
min

10 1700
min

5 1800
min

Mag. Check Adjustment Required: At completion of ground run:

Power Check 1. Visually inspect engine

Idle Check 2. Check oil level

Page 146, Section 72-60 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-09

Table 72-60-09C. IO-390-A1A6 Test Flight Chart

Flight Test after Top Overhaul or Cylinder Change with New Rings

1. Test fly aircraft for one hour.

2. Use standard power for climb and at least 75% power for cruise.
3. Make climb shallow and at good airspeed for cooling.
4. Record engine instrument readings during climb and cruise.

Flight Test Record

Time r M Temperature Pressure Temperature Fuel Flow
p A
m P

Oil Cyl. Oil Fuel Inj. Amb Flow

Air

Climb

Cruise

Adjustments Required After Flight: After test flight:

NOTE: If oil consumption is excessive, remove the spark plugs and 1. Make careful visual inspection of engine.
check cylinder barrels for scoring.
2. Check oil level.

14. When the engine fires, move the “MIXTURE CONTROL” smoothly to
“FULL RICH.”

15. Move the magneto switch to “BOTH.”

Caution
If oil pressure is not indicated within 10 seconds, stop the engine and
determine the cause.

16. Operate the engine at 1000 rpm until a minimum oil temperature of 140°F
(60°C) is obtained.

17. Check the magneto drop-off and general operation of the engine.

18. Check the engine for any oil leaks. Any malfunction or oil leak should be
repaired immediately before continuing with run-in or testing.

19. Complete the test run according to Table 72-60-09D.

August 2008 Page 147, Section 72-60

Section 72-60-09 IO-390-A1A6 Maintenance and Overhaul Manual

Table 72-60-09D. Recommended Run-in Schedule

rpm Load Time (min) Remarks

1200 Prop load 10 Check magneto drop-

1500 Prop load 10 off. Do not exceed

1800 Prop load 10 125 rpm on either

2000 Prop load 10 magneto or 35 rpm

2200 Prop load 10 between magnetos.

2400 Prop load 10

Normal Rated* Prop load 15

Normal Rated* Prop load 60 Oil consumption run.

*See Table 72-60-08A.

72-60-09d Oil Consumption Run

The oil consumption run, made at the end of the run-in schedule, measures the
quality of the engine overhaul.

Note: The oil consumption run is not intended to be an indication of the

maximum oil consumption limits that are listed in the Table of Limits
(Appendix III). Excessive oil consumption may indicate improper
seating of piston rings, broken rings, inverted rings, stepped cylinder
barrel, or worn rings caused from run-in of an engine in which abrasives
have entered the induction system, or in which parts were improperly
cleaned prior to reassembly. Improper fits and clearances due to a lack of
thoroughness during inspection, repair and replacement, and assembly
procedures at overhaul may also be indicated by excessive oil
consumption.

Oil consumption can be determined using a scale tank through which the oil lines
pass and the scale reading taken at the beginning and end of the oil consumption
run. Oil consumption can also be determined by draining and weighing the oil
supply before and after the oil consumption run.

During the oil consumption run, the temperature of the oil must be held as
closely as possible to the limits in Table 72-60-09A. Oil consumption should not
exceed the amounts shown in Table 72-60-09A.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-09

72-60-09e Idle Speed and Mixture Adjustment

Refer to Figure 72-60-09-1. Two adjustments must be made on the throttle body
assembly for proper idling conditions.

Fuel injectors require adjustments to the idle speed and fuel mixture to provide
smooth and economical engine operation. Complete the following steps to adjust
the idle speed and fuel mixture.

1. Start the engine and warm up in the usual manner until the oil and cylinder
head temperatures are normal.

2. Check the magnetos. If the “mag drop” is normal, continue to Step 3.

3. Set the throttle stop screw so that the engine idles at the airframe manufac-
turer’s recommended idling rpm. If the rpm changes appreciably after
making the idle mixture adjustment in the following steps, readjust the idle
speed to the desired rpm.

Figure 72-60-09-1. RSA-5AD1 Fuel Injector

August 2008 Page 149, Section 72-60

Section 72-60-09 IO-390-A1A6 Maintenance and Overhaul Manual

4. When the idling speed has been stabilized, move the cockpit mixture control
lever with a smooth, steady pull toward the IDLE CUT-OFF position and
observe the tachometer for any changes during the leaning process. Care
must be exercised to return the mixture control to the FULL RICH position
before the rpm can drop to a point where the engine cuts out. An increase of
more than 50 rpm while “leaning out” indicates an excessively rich idle
mixture. An immediate decrease in rpm (if not preceded by a momentary
increase) indicates that the mixture is too lean.

5. If either the “too rich” or “too lean” indications are present, turn the idle
mixture adjustment in the direction required for correction, and check this
new position by repeating the above steps. Make additional adjustments as
necessary until a check results in a momentary pick-up of approximately
50 rpm. Each time the adjustment is changed, the engine should be run up to
2000 rpm to clear the engine before proceeding with the rpm check. Make a
final adjustment to the idle speed adjustment to obtain the desired idling rpm
with closed throttle. This method attempts to reach a setting that will obtain
maximum rpm with a minimum manifold pressure. In case the setting does
not remain stable, check the idle linkage. Any looseness in the linkage would
cause erratic idling. In all cases, make allowances for the effect of weather
conditions and field altitude upon idling adjustments.

72-60-09e1 Idle Air Bleed Adjustment

If a satisfactory idle speed cannot be obtained as directed above, move the
mixture control lever toward the idle cut-off position with a smooth, steady
pulling motion while watching the tachometer. An increase of more than 50 rpm
indicates an excessively rich mixture. An immediate decrease in rpm (if not
preceded by a momentary increase in rpm) indicates that the mixture is too lean.

If the mixture is too rich, turn the idle air bleed adjustment screw
counterclockwise. If the mixture is too lean, turn the idle air bleed adjustment
screw clockwise. Run the engine up to 2000 rpm after each adjustment to clear
the engine before rechecking. Continue adjusting the idle air mixture screw until
a check results in a pick up of no less than five nor more than ten rpm running the
engine up to 2000 rpm between each adjustment. Refer to Table 72-60-09E.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 72-60-09

Table 72-60-09E. Engine Run-In after Overhaul

Revolutions Per Minute (rpm)

2700 1000 1200 1500 1800 2000 2200 2400 2500 2500

Time Until oil 10 10 10 10 10 15 60

(min) pressure
reaches Oil
140°F Consumption
(60°C) Run

MAP
(in. hg.)

Oil 55-95
Operating
Pressure
(psi)
235°F
Oil Inlet
(113°C)
Temp.
max.
permis-
sible
180°F
(82°C)
max.
allow-
able
Max. Cyl. 475°F
Head (246°C)
Temp.
(bayonet
location)

Fuel Press. 14 - 45
(at inlet to psi
injector)

Remarks

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IO-390-A Series Maintenance and Overhaul Manual Section 73-00-01

73-00-00 ENGINE FUEL AND CONTROL MAINTENANCE

73-00-01 GENERAL DESCRIPTION
The fuel distribution system is composed of a fuel pump, a fuel manifold (or
spider), fuel nozzles, a fuel filter, and fuel lines and fittings.

The Lycoming IO-390-A Series engine employs a Bendix RSA-5AD1 fuel

injector for fuel control, which operates on the principle of using airflow forces
to proportionally control the amounts of fuel and air that flow to the engine. The
fuel is distributed to each cylinder by means of a fuel flow manifold, and
vaporization takes place at the cylinder intake ports.

73-00-01a Fuel Recommendations

Always use the fuel specified in your Lycoming IO-390-A Series engine.
However, if the specified fuel is not available, a higher grade may be used.

Note: Isopropyl alcohol in amounts not to exceed 1% by volume may be added

to the fuel to prevent ice formation in fuel lines and tanks. Although
approved for use in Lycoming engines, isopropyl alcohol should not to
be used in the aircraft fuel system unless recommended by the aircraft
manufacturer.

Caution
Never use automotive fuel in aircraft engines, regardless of its octane or
advertised features because of the corrosive effect of its chlorine content,
and because of vapor lock that could result from its high vapor pressure.
Any fuel used in this engine must conform to ASTM-D910 or MIL-G-
5572F specifications.

Revised June 2009 Page 1, Section 73-00

Section 73-00-01 IO-390-A1A6 Maintenance and Overhaul Manual

Table 73-00-01. Specified Fuel Grade Comparison Chart

Current Commercial Fuel Grades Current Military Fuel Grades

(ASTM-D910-75) (MIL-G-5572F)

Grade Color Max. TEL Grade Color Max. TEL

ml/US gal. ml/US gal.

*100LL Blue 2.0 - - -

100 Blue 2.0 - - -

*Grade 100LL fuel in some countries is colored green and is designated as 100L.

73-00-01b Fuel Capacity

The capacity of the fuel tank supplied with this aircraft is not determined by
Lycoming. For additional information, consult your aircraft manual.

Page 2, Section 73-00 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 73-10-01

73-10-01 FUEL DISTRIBUTION

Check the integrity of fuel lines and fittings before each flight and repair any
leaks. If a hose or fitting in the fuel distribution system requires repair or
replacement, consult the parts manual for the appropriate replacement hose or
fitting.

Caution
Use only fuel-soluble lubricant such as clean engine oil or Loctite
Hydraulic Sealant as a thread compound. Do not use any other type of
thread compound.

73-10-01a Fuel Line Routing and Clamping

Refer to Section 72-60-08f4.

73-10-01b Fuel Pump Replacement

The fuel pump is mounted on the accessory housing. No maintenance is required
for the fuel pump; however, replacement may be necessary. Refer to Figure 73-
10-01-1.

Caution
As a means of reducing wear on fuel pump shaft, it is recommended that
Texaco Molytex type “O” (or equivalent) grease be applied to drive
spline before assembly of pump to engine.

Figure 73-10-01-1. Fuel Pump Replacement

August 2008 Page 1, Section 73-10

Section 73-10-01 IO-390-A1A6 Maintenance and Overhaul Manual

1. Use a wrench on the hex nut fitting to disconnect the fuel pump/fuel injector
line at the elbow.

2. Insert threaded plugs into the open ends of the fitting and line to prevent dirt,
dust or other contaminants from entering the fuel system.

3. Remove the elbow from the fuel pump.

4. Disconnect the fuel pump/fuel injector line at the elbow and insert a threaded
plug into that line.

5. Inspect the threaded areas of the elbow for stripped or damaged threads. If
any damage is apparent, replace the elbow. Refer to Lycoming Parts Catalog
PC-409-1 for correct replacement part.

6. Clean the elbow in solvent and dry with compressed air.

7. Remove the nuts, lockwashers, and plain washers from the studs that attach
the fuel pump to the accessory housing.

8. Replace the fuel pump and reassemble in the reverse order. Tighten the nuts
onto the studs to 100 in.-lb.

Caution
Exercise care in handling the gasket. It is extremely fragile.

9. Remove any spilled fuel or solvent in accordance with federal, state, and
local environmental regulations.

73-10-01c Fuel Nozzles

Fuel nozzles can become clogged with a type of varnish from old fuel or from
precipitate particles that are almost invisible to the naked eye. Should the engine
suddenly start to run roughly, a possible cause could be clogged fuel nozzles.
Complete the following steps, in the order given, to remove, clean, and replace
fuel nozzles.

1. Examine the nozzle lines for damage or wear. If the nozzle lines are worn or
damaged, replace the lines by unscrewing the lines from the flow divider.

2. Remove the nozzle assembly from the individual fuel lines using a wrench.

3. Insert a plug into the open end of each line to prevent dirt, dust or other
contaminants from entering the fuel lines.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 73-10-01

4. Remove the nozzles from the cylinders.

Caution
Never use a sharp tool such as a wire or pin to clean out a nozzle.
Damage to the inlet and outlet fuel restrictors could result which would
change the fuel flow.

5. Submerge the nozzles in Hoppe’s Gun Cleaning Solvent #9 or equivalent and

allow to soak briefly.

6. Remove the nozzles from the solvent and dry with clean, compressed air.

7. Remove the plugs from the fuel injection lines and replace them with the
cleaned nozzles using 50 in.-lb.

8. Remove any spilled gasoline or solvent in accordance with federal, state, and
local regulations.

73-10-01d Fuel Filter

Any fuel filtration system installed between the fuel tank and the fuel pump is
provided by the airframe manufacturer. Consult the airframe maintenance manual
for additional information.

73-10-01e Air Intake Ducts and Filters

This system is provided by the airframe manufacturer. Consult the airframe
maintenance manual for additional information.

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IO-390-A1A6 Maintenance and Overhaul Section 73-20-01

73-20-01 FUEL CONTROL

73-20-01a Fuel Injector

Fuel control is not repairable. Replace with a serviceable part. Fuel control is
provided by a RSA-5AD1 fuel injection system. Maintenance for this unit
consists of removing, cleaning, and replacing the 74 micron inlet screen and the
strainer O-ring.

73-20-01a1 Cleaning and Replacement of Inlet Screen and Strainer O-rings

1. Using a wrench on the hex fitting, disconnect the fuel supply line from the
fuel inlet port of the fuel injector. Install a plug into the fuel supply line to
minimize the possibility of fuel spills and to prevent any contaminants from
entering the fuel supply system.

Note: Always remove the screen from the inlet side only or dirt could enter the
injector unit.

2. Remove the inlet screen from the housing and examine it for distortions or
holes. If either condition is apparent, replace the inlet screen. Remove the
O-ring from the end of the inlet screen. Discard the O-ring. If the inlet screen
is intact, remove the O-ring from the end of the inlet screen. Discard the
O-ring. Clean the screen by soaking it briefly in solvent.

3. Remove the inlet screen from the solvent and dry with clean, compressed air.

4. Install a new O-ring on the end of the inlet screen and insert the inlet screen
into the fuel injector housing.

5. Tighten it to 60 to 70 in.-lb. torque. Remove the plug from the fuel supply
line and reconnect the line.

6. If any gasoline or solvent has been spilled, clean it up in accordance with

Federal, State, and Local regulations.

73-20-01a2 Idle Speed and Mixture Adjustments

Fuel injectors require adjustments to the idle speed and fuel mixture to provide
smooth and economical engine operation. Complete the following steps to adjust
the idle speed and fuel mixture.

1. Start the engine and warm up in the usual manner until the oil and cylinder
head temperatures are normal.

2. Check the magnetos. If the “mag drop” is normal, continue to Step 3.

August 2008 Page 1, Section 73-20

Section 73-20-01 IO-390-A1A6 Maintenance and Overhaul Manual

3. Set the throttle stop screw so that the engine idles at the airframe manufac-
turer’s recommended idling rpm. If the rpm changes appreciably after
making the idle mixture adjustment in the following steps, readjust the idle
speed to the desired rpm.

4. When the idling speed has been stabilized, move the cockpit mixture control
lever with a smooth, steady pull toward the IDLE CUT-OFF position and
observe the tachometer for any changes during the leaning process. Care
must be exercised to return the mixture control to the FULL RICH position
before the rpm can drop to a point where the engine cuts out. An increase of
more than 50 rpm while “leaning out” indicates an excessively rich idle
mixture. An immediate decrease in rpm (if not preceded by a momentary
increase) indicates that the mixture is too lean.

5. If either the “too rich” or “too lean” indications are present, turn the idle
mixture adjustment in the direction required for correction, and check this
new position by repeating the above steps. Make additional adjustments as
necessary until a check results in a momentary pick-up of approximately
50 rpm. Each time the adjustment is changed, the engine should be run up to
2000 rpm to clear the engine before proceeding with the rpm check. Make a
final adjustment to the idle speed adjustment to obtain the desired idling rpm
with closed throttle. This method attempts to reach a setting that will obtain
maximum rpm with a minimum manifold pressure. In case the setting does
not remain stable, check the idle linkage. Any looseness in the linkage would
cause erratic idling. In all cases, make allowances for the effect of weather
conditions and field altitude upon idling adjustments.

73-20-01a3 Fuel Injector Removal

1. Disconnect the fasteners which hold the fuel injector to the engine.

2. Disconnect the fuel supply line from the fuel inlet port of the fuel injector
using a wrench on the hex fitting.

3. Install a plug into the fuel supply line to minimize the possibility of fuel
spills and to prevent any contaminants from entering the fuel supply system.

73-20-01a4 Cleaning
1. Disconnect the fuel supply line from the fuel inlet port of the fuel injector
using a wrench on the hex fitting.

2. Install a plug into the fuel supply line to minimize the possibility of fuel
spills and to prevent any contaminants from entering the fuel supply system.

3. Remove the inlet screen from the housing and examine it for distortions or
holes. If either condition is apparent, replace the inlet screen.

Page 2, Section 73-20 August 2008

IO-390-A1A6 Maintenance and Overhaul Section 73-20-01

4. If the inlet screen is intact, remove the O-ring from the end of the inlet
screen. Discard the O-ring according to federal, state, and local
environmental mandates.

5. Clean the screen by soaking it briefly in unleaded gasoline or Varsol cleaning

fluid.

6. Remove the inlet screen from the solvent and dry with clean, compressed air.

7. If any gasoline or solvent has been spilled, clean it up in accordance with

federal, state, and local regulations.

73-20-01a5 Fuel Injector Nozzles

1. Remove the nozzle assembly from the individual fuel lines using a wrench.

2. Insert a plug into the open end of each line to prevent dirt, dust, or other
contaminants from entering the fuel lines.

Caution
Never use a sharp tool such as a wire or pin to clean out a nozzle.
Damage to the inlet and outlet fuel restrictors could result.

3. Submerge the nozzles in Hoppe’s Gun Cleaning Solvent #9 or equivalent and

allow to soak briefly.

4. Remove the nozzles from the solvent and dry with clean, compressed air.

5. If any gasoline or solvent has been spilled, clean it up in accordance with

federal, state, and local environmental regulations.

73-20-01a6 Inspection

1. Inspect the throttle lever and linkage for damage or wear.

2. Check the fuel manifold assembly for damage or leaks.

3. Inspect all other lines and fittings for damage or leaks.

73-20-01a7 Nozzle Assembly

1. Examine the nozzles for damage or restrictions.

73-20-01a8 Fuel Flow Check

1. Disconnect the fuel lines and remove the nozzles from the cylinders.

August 2008 Page 3, Section 73-20

Section 73-20-01 IO-390-A1A6 Maintenance and Overhaul Manual

2. Attach the nozzles to the fuel lines and direct the nozzles into four clear
containers of equal size.

3. Turn the boost pump on and move the throttle and mixture control full
forward.

4. Allow approximately 4 to 6 ounces of fuel to flow into each container. Close

the throttle and mixture and turn off the boost pump.

5. Place all four containers on a flat surface. Check the level of the fuel. All
containers should have the same amount of fuel. A container having less fuel
is an indication of a restriction.

Note: While flowing the fuel, be sure that the stream from all four lines is solid,
steady and even.

Page 4, Section 73-20 August 2008

IO-390-A1A6 Maintenance and Overhaul Manual Section 74-00-01

74-00-00 IGNITION SYSTEM MAINTENANCE

74-00-01 GENERAL DESCRIPTION
The ignition system for this engine includes two Slick magnetos, a Slick ignition
harness, long reach spark plugs, and a Kelly Aerospace starter.

74-00-01A. Ignition System Components

Ratio to
Direction of Crankshaft
Component Model Rotation Rotation

Slick Magneto 4345 (Left) Clockwise* 1.0:1

4370 (Right)

Kelly Aerospace 12 Volt Counterclockwise* 16.556:1

Starter†

Alternator† Clockwise* --

* All rotations are viewed from the anti-propeller end of the engine

† - For optional starters and alternators see the latest revision of Lycoming
Service Instruction No. 1154.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 74-10-01

74-10-00 ELECTRICAL POWER SUPPLY SYSTEM MAINTENANCE

74-10-01 GENERAL DESCRIPTION
Electrical power supply is provided by two Slick Magnetos, a Kelly Aerospace
starter, and an alternator. For optional starter and alternators see the latest
revision of Lycoming Service Instruction No. 1154.

These components are not repairable. Replace with a serviceable part.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 74-10-02

74-10-02 RETARD MAGNETOS

The magnetos incorporate a retard contact assembly. The magnetos spin a
magnet at 1-1/2 times the engine speed, thus producing six sparks through 720
degrees of rotation. A battery operated starting vibrator provides electrical energy
for starting, regardless of engine cranking speed. The retard ignition is in the
form of a shower of sparks rather than a single spark.

The engine firing order is 1-3-2-4. The spark advance is 20°BTC. The magneto
drive is clockwise and the ratio to crankshaft and rotation is 1.000:1.

The magneto is not repairable. Replace with a serviceable part.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 74-10-03

74-10-03 ALTERNATOR
There are no regularly scheduled maintenance procedures for the alternator.
Lycoming recommends that the alternator be replaced as needed.

The alternator is not repairable. Replace with a serviceable part.

An improperly tensioned alternator drive belt can slip, wear prematurely, and
reduce electrical output. Belt tension is to be checked during periodic
maintenance and anytime a belt is replaced.

There are three satisfactory methods of checking belt tension; however, the first
method described is the quickest and simplest.

1. Torque Method: This method of checking belt tension consists of measuring

the torque required to slip the belt at the small pulley and is accomplished as
follows:

a. Secure the propeller to prevent rotation of the engine.

b. Apply a torque indicating wrench to the nut that attaches the pulley to the
alternator and turn it in a clockwise direction. Observe the torque shown
on the wrench at the instant the pulley slips.

c. Check torque indicated in step a. with torque specified in the following

chart. Adjust belt tension accordingly.

Width of Belt Condition Torque Indicated at Alternator Pulley

⅜ inch New 11 to 13 ft. lbs.

⅜ inch Used 7 to 9 ft. lbs.
½ inch New 13 to 15 ft. lbs.
½ inch Used 9 to 11 ft. lbs.
11 mm New 22 to 24 ft. lbs.
11 mm Used 15 to 17 ft. lbs.
Note: The higher tension specified for a new belt is to compensate for the
initial stretch that takes place as soon as it is operated. These higher
tension values should not be applied to belt, which has been used
previously.

Note: When a new belt is installed, check the belt tension after the first 1 to 1.5
hours of operation and reset to used limits. Check and reset to used limits
again after 8 hours of operation. Check each periodic inspection
thereafter.

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Section 74-10-03 IO-390-A1A6 Maintenance and Overhaul Manual

2. Deflection Method: Belt tension may be checked by measuring the amount

of deflection caused by a predetermined amount of tension; this is
accomplished in the following manner:

a. Attach the hook of a small spring-scale to the belt at the approximate

mid-point between the ring gear support and the alternator.

b. Pull on the scale until a reading of 14 pounds is obtained. (10 pounds for
used belts.)

c. Measure the distance the belt has moved with the 10 or 14 pound load
applied. The distance (deflection) should be 5/16 inch. If less than 5/16
inch, belt is too tight.

3. Belt Tension Gage: A belt tension gage that measures belt tension by
indicating the amount of deflection of the belt under a preset spring load is
available as Lycoming tool number ST-131.

Alternator drive is clockwise.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 74-10-04

74-10-04 STARTER
The starter drive ratio from the Bendix drive pinion to crankshaft is 16.556:1.

Starter rotation is clockwise.

For optional starter and alternators see the latest revision of Lycoming Service
Instruction No. 1154.

The only regularly scheduled maintenance procedure that applies is routine

inspection for Kelly Aerospace starters. Refer to Section 05-20-03.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 74-20-01

74-20-00 ELECTRICAL POWER DISTRIBUTION SYSTEM

MAINTENANCE
74-20-01 GENERAL DESCRIPTION
Electrical power is distributed by radio-shielded, long-reach spark plugs and by a
Slick ignition harness.

Lycoming recommends that these items be replaced as specified in Section 05-

20-00, Scheduled Maintenance Checks.

Overhaul, removal, and reassembly instructions are found in Section 72-60-03.

The airframe manufacturer determines the final routing of the wiring harness and
location of the clamping hardware.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 74-20-02

74-20-02 IGNITION HARNESS

The Slick ignition harness is an all-weather, shielded harness constructed with
braid over wire.

The only regularly scheduled maintenance procedure that applies to the Slick
harness is routine inspection. Refer to Section 05-20-03.

1. Inspect the harness for signs of chaffing, cracks in the all-weather shielding,
or worn leads. Replace the harness if any leads exhibit chaffing, cracks, or
wear.

2. Examine the harness connections. Make certain the harness connections are
secure. Tighten the leads if any connections are loose.

3. Ensure security of ignition harness mounting clamps.

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IO-390-A1A6 Maintenance and Overhaul Manual Section 74-20-03

74-20-03 SPARK PLUGS

74-20-03a Removal and Installation

Removal
Remove plugs using a 7/8 inch deep recess socket.

Installation
When installing or reinstalling a plug, use a 7/8 inch deep recess socket. Tighten
to 420 in.-lb. (35 ft.-lb.).
Note: Any time a plug is installed or reinstalled, a new gasket should be used.
Do not reuse gaskets.

This engine is equipped with radio-shielded, long-reach spark plugs.

74-20-03b Maintenance Procedures

Regularly scheduled maintenance procedures for the spark plugs consists of
rotating the spark plugs at 25 to 50 hour intervals, spark plug cleaning, and
regapping as needed if there is evidence of spark plug fouling.

1. Confirm that the P-leads are securely attached to the magneto condenser
studs. Torque P-lead nut to 13-15 in.-lb. as required.

2. Rotate the spark plugs by moving the bottom plugs to the upper position
whenever operational ground checks indicate evidence of spark plug fouling.
See Table below.

SPARK PLUG ROTATION

Interchange

#1 Top with #4 Bottom

#2 Top with #3 Bottom

#3 Top with #2 Bottom

#4 Top with #1 Bottom

3. Remove spark plug connector nuts and examine spark plug cable leads and
ceramics for corrosion and deposits. Corrosion and deposits are evidence of
leaking spark plugs or improper cleaning of the spark plug walls or connector
ends.

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Section 74-20-03 IO-390-A1A6 Maintenance and Overhaul Manual

4. Recondition or replace affected spark plugs as necessary, being certain plugs

are of the correct heat range.

5. Clean the cable ends, spark plug walls, and ceramics with a clean lint-free
cloth moistened with methyl-ethyl ketone (MEK), acetone, or wood alcohol.

6. Replace any broken, cracked, deformed, or corroded parts.

7. Dry all parts using compressed air.

8. Visually inspect the ignition harness for evidence of chaffing or

deterioration. Replace the harness assembly if any leads are worn, damaged,
or broken. Refer to section 74-20-01a.

9. Ensure the security of ignition harness mounting clamps.

10. Verify that the spark plug and magneto terminal connections are tight.

11. Correct any discrepancies noted.

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IO-390-A1A6 Maintenance and Overhaul Manual Appendix I

APPENDIX I: PARTS CATALOG

Appendix I: Parts Catalog for this Maintenance and Overhaul Manual is
Lycoming Part Number PC-409-1.

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IO-390-A1A6 Maintenance and Overhaul Manual Appendix II
APPENDIX II: ENGINE PERFORMANCE DATA
Curve Number 13578. Actual Horsepower
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Appendix II IO-390-A1A6 Maintenance and Overhaul Manual

Curve Number 12885A. Fuel Flow Versus Nozzle Pressure

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IO-390-A1A6 Maintenance and Overhaul Manual Appendix II

Curve Number 13579. Fuel Flow Versus Power

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IO-390-A1A6 Maintenance and Overhaul manual Appendix III

APPENDIX III: TABLE OF LIMITS

INTRODUCTION
This Table of Limits is provided as a guide to all service and maintenance
personnel engaged in the repair and overhaul of Lycoming Aircraft Engines.
Most of the material contained herein is subject to revision; therefore, any
question regarding a specific limit or the incorporation of limits shown should be
addressed to the Lycoming factory for clarification.

DEFINITIONS
Ref. The numbers in the first column headed “Ref.” are
(1st column) shown as reference numbers to locate the area
described in the “Nomenclature” column. This
number will be found in a diagram at the end of each
section, indicating a typical section where the limit
is applicable.

Nomenclature This is a brief description of the parts or fits

(2nd column) specified in the adjacent columns and indicated in
the diagram at the end of each section.

Dimensions The dimensions shown in column 3 are the

(3rd and 4th columns) minimum and maximum dimensions for the part as
manufactured. The dimensions shown in column 4
indicate the limit that must not be exceeded. Unless
it can be restored to serviceable size, any part that
exceeds this dimension must not be reinstalled into
an engine.

Clearance Like the dimensions shown in columns 3 and 4, the

(5th and 6th columns) clearance represents the fit between two mating
surfaces as controlled during manufacture and as a
limit for permissible wear. Clearances may
sometimes be found to disagree with limits for
mating parts; for example, the maximum diameter of
a cylinder minus the minimum diameter of a piston
exceeds the limit for piston and barrel clearance. In
such instances, the specified maximum clearance
must not be exceeded.

In some instances, where a parts revision has caused a dimensional or tolerance

change, the superseded dimensional data have been deleted from the list;
provided compliance with the change is not mandatory.

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Letters of the alphabet and numbers are used as symbols throughout the Table of
Limits to represent specific interpretations and to designate engine models.
Letters in parentheses refer to dimensional characteristics; letters (or combina-
tions of letters and numbers) without parentheses indicate engine models. They
are listed below with their separate definitions.

(A) These fits are either shrink fits controlled by machining, fits that may
readily be adjusted, or fits where wear does not normally occur. In each
case, the fit must be held to manufacturing tolerance.

(B) Side clearance on piston rings must be measured with face of ring flush
with piston.

(E) Permissible wear of the crankshaft (rod and main bearing journals) to be
minus 0.0015 on the diameter.

Section 1 – Crankcase, Crankshaft, and Camshaft

Dimensions (in.) Clearance (in.)

Ref. Mfr. Min. Service Mfr. Min. Service
Nomenclature & Max. Max & Max. Max
500 Main Bearings and Crankshaft 0.0015L
0.0045L 0.0060L
Diameter of Main Bearing 2.6245
Journal on Crankshaft 2.626 (E)
(2-5/8 in. Main)
Diameter of Front Main Bearing 2.6245
Journal on Crankshaft 2.6255 (E)
(2-5/8 in. Main)
Crankcase Bearing Bore Diameter 2.816
2.817 2.8185
501 Connecting Rod Bearing and 0.0008L
Crankshaft 0.0038L 0.0050L
501 Diameter of Connecting Rod 2.1235
Journal on Crankshaft 2.125 (E)
(2-1/8 in.)
Connecting Rod Bearing Bore 2.2870
Diameter (2-1/8 in.) (Measured at 2.2875
Axis 30° on Each Side)

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IO-390-A1A6 Maintenance and Overhaul manual Appendix III

Dimensions (in.) Clearance (in.)

Ref. Mfr. Min. Service Mfr. Min. Service
Nomenclature & Max. Max & Max. Max
502 Connecting Rod − Side Clearance 0.004L
0.010L 0.016L
503 Connecting Rod − Alignment 0.010 in 10 in.
504 Connecting Rod − Twist 0.012 in 10 in.
505 Mounted on No. 1 and 4 Journals 0.002 0.002
Max. Run-Out No. 2 Journal
Mounted on No. 1 and 4 Journals 0.005 0.0075
Max. Run-Out No. 3 Journal
Mounted on No. 2 and 4 Journals 0.003 0.0045
Max. Run-Out No. 3 Journal
506 Crankshaft and Crankcase Front 0.009L
End Clearance 0.018L 0.026L
507 Clearance − Front Face of 0.002
Crankshaft Oil Slinger to Front 0.017L (A)
Face of Recess in Crankcase
(Crankshaft against Thrust Face)
508 Crankshaft Prop. Flange Run-Out 0.002 0.005
509 Starter Ring Gear and Support 0.014T
0.022T (A)
510 Crankshaft Timing Gear and 0.0005T
Crankshaft 0.0010L (A)
511 Tappet Body and Crankcase 0.0010L
0.0033L 0.004L
OD of Tappet 0.8428
0.842 0.7166
ID Tappet Bore in Crankcase 0.8445
0.8437 0.7203
512 Tappet Plunger Assembly and
0.0010L
Body 0.0047L 0.0067L
513 Tappet Socket and Body 0.002L
0.005L 0.007L
514 Camshaft and Crankcase 0.002L
0.004L 0.006L
515 Camshaft − End Clearance 0.002L
0.009L 0.015L

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Dimensions (in.) Clearance (in.)

Ref. Mfr. Min. Service Mfr. Min. Service
Nomenclature & Max. Max & Max. Max
516 Camshaft Run-Out at Center 0.000
Bearing Journal 0.001 0.006
517 Counterweight Bushing and 0.0013T
Crankshaft 0.0026T (A)
518 Counterweight Roller − End 0.007L
Clearance 0.025L 0.038L
519 Counterweight and Crankshaft − 0.003L
Side Clearance 0.013L 0.017L
520 Counterweight Bore and Washer 0.0002L
OD 0.0030L (A)
521 ID of Counterweight Bushing 0.7485
0.7505 0.7512
th
522 OD of Counterweight Roller – 8 0.7166
Order 0.7161
OD of Counterweight Roller – 6.3 0.6915
Order 0.6910

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IO-390-A1A6 Maintenance and Overhaul manual Appendix III

Section 2 – Cylinders

Dimensions Clearance
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
600 Connecting Rod and Connecting Bushing to Be Burnished in Place.
Rod Bushing
Finished ID of Connecting Rod 1.1254
Bushing 1.1262
601 Length between Connecting Rod 6.7485
Bearing Centers 6.7515
602 Connecting Rod Bushing and 0.0008L
Piston Pin 0.0021L 0.0025L
603 Piston Pin and Piston 0.0003L
0.0014L 0.0018L
Diameter of Piston Pin Hole in 1.1249
Piston 1.1254
Diameter of Piston Pin 1.1241
1.1246
604 Piston Pin and Piston Pin Plug 0.0002L
0.0010L 0.002L
Diameter of Piston Pin Plug 1.1242
1.1247
606 Piston Ring and Piston − Side 0.0025L
Clearance (Top Ring Comp.) Half 0.0055L 0.008L(B)
Wedge
Piston Ring and Piston − Side 0.000
Clearance (2nd Ring Comp.) 0.004L 0.006L(B)
Full or Half Wedge
Piston Ring and Piston − Side 0.002L
Clearance (Oil Regulating) 0.004L 0.006L(B)
607 Piston Ring Gap (Compression) 0.045
Nitrided 0.055 0.067
Piston Ring Gap (Oil Regulating) 0.015
0.035 0.047
The Ring gap is measured within 4 in. from the bottom. Ring gap at top of travel must not be less than
0.0075 in.

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Dimensions Clearance
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
Maximum
Cyl. Barrel Clearance
Type Piston
Minimum Piston Type of of Max. Skirt &
Piston Number Diameter Piston Surface Diameter Cylinder
608 14E22396 5.3125 Cast-Cam P-C-N 5.320 0.018L
5.3095 5.3175
609
610
Notes for Section 2 ⎯ Cylinders
To find the average diameter of a cylinder in an Maximum taper and out-of-round permitted for a
area 4 in. above the bottom of the barrel: cylinder in service is 0.0045 in.
1. Measure diameter at right angles from plane in
which valves are located. Piston diameter at the top is measured at the top
2. Measure diameter through the plane in which ring land (between the top and second compression
valves are located. ring grooves) at a right angle to the piston pin hole.
Piston diameter at the bottom is measured at the
3. Add both diameters.
bottom of the piston skirt at right angles to the
4. Divide this sum by 2 to get the average piston pin.
diameter of the cylinder.
Cylinder Barrel: P = plain steel, N = nitride
To find the average out-of-round, measure the
hardened, C = chrome plated.
diameter of the cylinder in an area 4 in. above the
bottom of the barrel:
1. Measure the diameter at right angles from the
plane in which the valves are located.
2. Measure the diameter through the plane in
which the valves are located.
3. The difference between the diameters must not
exceed 0.0045 in.

Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
611 Exhaust Valve Seat and Cylinder 0.0045T
Head 0.008T (A)
OD Exhaust Seat 1.936
1.935

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IO-390-A1A6 Maintenance and Overhaul manual Appendix III

Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
611 ID Exhaust Seat Hole in 1.928
Cylinder Head 1.926
612 Intake Valve Seat and Cylinder 0.0065T
Head 0.010T (A)
OD Intake Seat 2.2899
2.2889
ID Intake Seat Hole in Cylinder 2.282
Head 2.280
613 Exhaust Valve Guide and 0.001T
Cylinder Head 0.0025T (A)
OD Exhaust Valve Guide 0.6633
0.6638
ID Exhaust Valve Guide Hole in 0.6613
Cylinder Head 0.6623
614 Intake Valve Guide and Cylinder 0.0010T
Head 0.0025T
OD Intake Valve Guide 0.5933
0.5938
ID Intake Valve Guide Hole in 0.5913
Cylinder Head 0.5923
615 Exhaust Valve Stem and Valve 0.0030L
Guide (Angle Valve Heads) 0.0050L (A)
OD Exhaust Valve Stem (Angle 0.4957
Valve Heads) 0.4965 0.4937

Finished ID Exhaust Valve 0.4985

Guide (Angle Valve Heads) 0.4995
1/2 inch diameter exhaust valves may have exhaust valve guides that are .003 in. over the
maximum inside diameter limit, anytime up to 300 hours of service. After 300 hours of service,
inside diameter of exhaust valve guide may increase .001in. during each 100 hours of operation
up to the recommended overhaul time for the engine, or not to exceed .015 inch over the basic
I.D. See latest revision of Service Instruction No. 1009 for recommended overhaul time.
616 Intake Valve Stem and Valve 0.0010L
Guide 0.0028L 0.006L
OD Intake Valve Stem 0.4022
0.4030 0.4010
Finished ID Intake Valve Guide 0.4040
0.4050
617 Intake and Exhaust Valve and 0.000L
Valve Cap Clearance (Rotator 0.004L 0.005L
Type Small Diameter Head)

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Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
618 Dry Tappet Clearance 0.028
0.080
619 Finished ID of Valve Rocker 0.6246
Shaft (Bushing) in Cylinder 0.6261 0.6270
Head
Valve Rocker Shaft and Valve 0.0001L
Rocker Bushing 0.0013L 0.0025L
620 Finished ID of Rocker Arm 0.6252
Bushing 0.6263 0.6270
OD Valve Rocker Shaft 0.6241 0.0007L
0.6245 0.6231 0.0017L 0.004L
621 Valve Rocker Bushing and Bushing must be
Valve Rocker burnished in place.

622 Valve Rocker Shaft Bushing 0.7380

Hole in Cylinder Head 0.7388

Valve Rocker Shaft Bushing and 0.0022T

Cylinder Head 0.0038T (A)
623 Valve Rocker and Cylinder Head 0.005L
− Side Clearance 0.013L 0.016L
625 Intake Valve Guide Height 0.705
0.725
Measure the Valve
Guide Height from the
Valve Spring Seat
Counterbore in the
Cylinder Head to the
Top of the Valve Guide.
Exhaust Valve Guide Height 0.765
0.785
Measure the Valve
Guide Height from the
Valve Spring Seat
Counterbore in the
Cylinder Head to the
Top of the Valve Guide.

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Section 3 ⎯ Gear Train Section−Oil Pump

Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
700 Oil Pump Drive Shaft and Oil 0.0010L
Pump Body 0.0025L 0.004L
701 Oil Pump Drive Shaft and 0.015L
Accessory Housing 0.030L 0.006L
703 Oil Pump Impellers - Diameter 0.002L
Clearance 0.006L 0.008L
704 Oil Pump Impeller - Side 0.002L
Clearance 0.0045L 0.005L
705 Oil Pump Impeller and Idler 0.001T
Shaft 0.003T (A)
706 Oil Pump Idler Shaft and Oil 0.0005L
Pump Body 0.0020L 0.003L
707 Oil Pump Idler Shaft and Oil 0.0010L
Accessory Housing 0.0025L 0.0035L

Section 3 – Gear Train Section-Fuel Pump

Dimensions Clearances
Ref. Nomenclature Mfr. Min. Service Mfg. Min. Service
& Max. Max. & Max. Max.
719 AC Fuel Pump Plunger and .0015L
Accessory Housing .003L .005L
720 Crankshaft Ider Gear and .001L
Crankshaft Idler Gear Shaft .003L .005L

724 Crankshaft Idler Gear – End .007L

Clearance .037L .052L

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IO-390-A Series Maintenance and Overhaul Manual Appendix III

Section 3  Gear Train SectionGovernor

Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
729 Front Governor Idler Gear and 0.0010L
Shaft 0.0025L 0.004L
731 Front Governor Gear and 0.0010L
Crankcase 0.0025L 0.004L
732 Front Governor Gear  End 0.008L
Clearance 0.016L 0.021L
733 Rear Governor Gear and Adapter 0.0010L
0.0025L 0.005L
734 Rear Governor Gear – End 0.002L
Clearance 0.024L 0.034L

Section 3  Gear Train SectionVacuum & Tachometer

Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
737 Vacuum Pump Gear and Adapter 0.010L
0.030L 0.0045L
738 Vacuum Pump Gear  End 0.010L
Clearance 0.057L 0.075L
739 Tachometer Drive Shaft and 0.0015L
Accessory Housing 0.0035L 0.006L

Section 3  Gear Train SectionMagneto, Generator, Starter

Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
758 Magneto Gear and Bushing 0.0015L
(S6LN-21 and S6LN-1227) 0.0035L 0.0055L

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IO-390-A1A6 Maintenance and Overhaul manual Appendix III

Section 4 ⎯ Backlash

Dimensions Clearances
Mfr. Min. Service Mfr. Min. Service
Ref. Nomenclature & Max. Max & Max. Max
800 Crankshaft and Vacuum Pump − 0.004
Backlash 0.015 0.020
803 Camshaft and Crankshaft Idler − 0.004
Backlash 0.015 0.020
804 Crankshaft and Crankshaft Idler 0.004
− Backlash 0.015 0.020
805 Magneto Drive and Crankshaft 0.004
Idler − Backlash 0.015 0.020
808 Oil Pump Impellers − Backlash 0.008
0.015 0.020
820 Hydraulic Pump and Crankshaft 0.004
Idler − Backlash 0.015 0.020
822 Propeller Governor Idler and 0.004
Camshaft − Backlash (Front 0.015 0.020
Governor)
823 Propeller Governor Drive and 0.004
Idler − Backlash (Bevel Gears) 0.008 0.015
(Front Governor)

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IO-390-A1A6 Maintenance and Overhaul manual Appendix III

Section 5 ⎯ Special Torque Requirements

Ref. Thread Size Nomenclature Torque Limits
900 Connecting Rod Bolts − Tighten 2.255 − 2.256 in.
to Length
903 Magneto Nut (To attach drive 120 − 300 in. lb
member to magneto) − Slick
904 Magneto Plate Screws (To attach 18-28 in. lb
harness to magneto)
905 Rocker Box Screws 50 in. lb
906 Exhaust Port Studs (Driving 40 in. lb min.
Torque)
907 Spark Plugs 420 in. lb
909 Alternator Pulley Nut 450 in. lb
910 Alternator Output Terminal Nut 85 in. lb
911 Alternator Auxiliary Terminal 30 in. lb
Nut
913 Piston Cooling Nozzle in 100 in. lb
Crankcase
914 Injector Nozzle in Cylinder Head 60 in. lb
915 Oil Filter (Throw Away Type) 240 in. lb
917 Thermostatic Bypass Valve 300 in. lb
918 Oil Pressure Relief Valve 300 in. lb
919 ¼ Hex Head and Below Hose Clamps (Worm Type) 20 in. lb
5/16 Hex Head and Above Hose Clamps (Worm Type) 45 in. lb
920 Cylinder Head Drain Back Hose 10 in. lb
Clamps
928 3/8-16 Cylinder Hold Down Studs 100 in. lb min.
(Crankcase Driving Torque)
½-13 Cylinder Hold Down Studs 250 in. lb min.
(Crankcase Driving Torque)
929 3/8-24 Cylinder Hold Down Nuts 300 in. lb
½-20 Cylinder Hold Down Nuts 600 in. lb
930 .3125-32 NEF-3B Fuel Injection Line Union Nut 25-50 in. lb

August 2008 III-19

Appendix III IO-390-A1A6 Maintenance and Overhaul Manual

Section 6 ⎯ Springs
Comp. Load
Length
Wire at Comp. Mfr. Mfr. Serv.
Lycoming Dia. Length Min. Max. Max.
Ref. Chart Nomenclature Part No. (in.) (in.) (lb) (lb) (lb min)
950 Outer Valve LW-11796 0.182 1.43 116 124 113
Springs
(Angle)
951 Auxiliary LW-11797 0.142 1.33 75 83 72
Valve Spring
(Angle)
952 Oil Pressure
Relief Valve
Spring
Identification
Lycom. Dye Free Length
Part No.
61084 None 2.18 0.054 1.30 8.5 9.5 8.3
68668 Purple 2.04 0.054 1.30 7.1 7.8 6.9
77467 Yellow 1.90 0.054 1.30 6.4 7.1 6.2
LW-11713 White 2.12 0.059 1.44 10.79 11.92 10.5
LW-18085 White & 1.93 0.067 1.44
Purple Dots

III-20 August 2008

IO-390-A Series Maintenance and Overhaul Manual Appendix III

Revised January 2010 III-21

Appendix III IO-390-A Series Maintenance and Overhaul Manual

III-22 Revised January 2010

IO-390-A Series Maintenance and Overhaul Manual Appendix III

Revised October 2010 III-23

Appendix III IO-390-A Series Maintenance and Overhaul Manual

III-24 Revised January 2010

IO-390-A Series Maintenance and Overhaul Manual Appendix III

Revised January 2010 III-25

Appendix III IO-390-A Series Maintenance and Overhaul Manual

III-26 Revised January 2010

IO-390-A Series Maintenance and Overhaul Manual Appendix III

STANDARD TORQUE
UNLESS OTHERWISE LISTED

Torque limits for propeller attaching bolts to be supplied by propeller aircraft manufacturer.

TABLE I TABLE II
BOLTS, SCREW AND NUTS PIPE PLUGS
Torque Torque Torque
Thread Thread Thread
In. Lb. Ft. Lb. In. Lb. Ft. Lb. In. Lbs.
10 49 ----- 1/2 900 75 1/16-27 NPT 40
1/4 96 ----- 9/16 1320 110 1/8-27 NPT 40
5/16 204 17 5/8 1800 150 1/4-18 NPT 85
3/8 360 30 3/4 3240 270 3/8-18 NPT 110
7/16 600 50 ----- ----- ----- 1/2-14 NPT 160
3/4-14 NPT 230
THIN NUTS (1/2 DIA. OF BOLT) – 1/2 LISTED TORQUE 1-11-1/2 315
NPT

TABLE III TABLE IV

FLEXIBLE HOSE OR TUBE FITTINGS STUDS MIN. DRIVING
TORQUE
Torque In. Lbs.
Aluminum Steel Torque In.
Tube Size Thread Alloy Threads Lbs.
(-3) 3/16 3/8 – 24 25 – 35 95 – 105 1/4-20 15
(-4) 1/4 7/16 – 20 50 – 65 35 – 150 5/16-18 25
(-5) 5/16 1/2 – 20 70 – 90 170 – 200 3/8-16 50
(-6) 3/4 – 16 230 – 260 450 – 500
(-10) 5/8 7/8 – 14 330 – 360 650 – 700

TABLE V
JAM NUT OR STRAIGHT THREAD O-RING BOSS
Tube Size Thread Torque Ft. Lbs.
-03 3/8 – 24 8–9
-04 7/16 – 20 13 – 15
-05 1/2 – 20 14 – 15
-06 9/16 – 18 23 – 24
-08 3/4 – 16 40 – 43
-10 7/8 – 14 43 – 48
-12 1-1/16 – 12 68 – 75
-14 1-3/16 – 12 83 – 90
-16 1-5/16 – 12 112 – 123
-20 1-5/8 – 12 146 – 161
-24 1-7/8 – 12 154 – 170
-32 2-1/2 – 12 218 – 240

Revised January 2010 III-27