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HORSEPOWER
MODEL 425A
JAKE BRAKE®
FOR CUMMINS NHANT ENGINES
One model fits most
pre-1988 Cummins
Big & Small Cam Engines
Adaptable to Fixed Timed
or STC engine controls
Three levels of retarding
for operating flexibility
Proven Jake Brake
technology
425A PERFORMANCE
FIXED TIMED
0
1100 1300 1500 1700 1900 2100
RPM
All horsepowers listed at SAE standard atmospheric conditions.
Retarding HP
by Engine Control MODEL 425A
JACOBS® ENGINE BRAKE FOR
CUMMINS NHINT ENGINES
ENGINE BRAKE MODEL _(Three housings, each controling two engine cylinders)
Overall Dimensions of Basic a
Engine Brake Housing bi
Height 25 64
Length 125 305
Wath 75 491
‘Added Engine Height! 25 64
Welght of Standard
Engine Brake Kit i ka
Shipping Weight 84 38
‘Added Vehicle Weight? 80 36
Number of Housings per Kit 3
1 Added height refers to overall vertical increase,
2 Because some engine brake components replace standard engine parts, added Vehicle Weight does not necessarily
‘equal weight of pro-installad Jacobs Engine Brake.
Torque Specifications
Exhaust Valve Crosshead Adjusting Screw Locknut 25 Ibtt. (34 Nem) «
Slave Piston Adjusting Screw Locknut 25 Ib. (34 Nem)
Rocker Housing Stud 70 bt. (95 Nem)
Engine Brake Hold-down Nut 60 Ibft. (80 Nm)
Rocker Lever Adjusting Screw Locknut 45 Ibft. (60 Nem)
Engine Brake Applications and Adjustment
Model Engine Slave Piston Adjustment ‘Slave Piston Adj. Tool P/N
425A Pre-1988 Big & Small Cam 0.018 in. 03087
with Divided Entry Turbo
425A Pre-1988 Big Cam 0.030 in. 15877
with Single Entry Turbo
FT (some* CPL Nos.)
425A Pre-1988 Small Cam 0.037 in. 15878
with Single Entry Turbo
with No Turbo
Pre-1988 Big Cam
with Single Entry Turbo (some* CPL. Nos.)
with STC (some* CPL Nos.)
*Refer to Installation Manual, P/N 15864, and Service Letter 342 for specific application information. q
FT = Fixed Timed STC = StepTiming Control
J , Jacobs®, Jako Breke® and Auto-Lash® are registered trademarks of Jacobs Vehicle Equipment Company.
‘Jake is a Marc. Rg. in Mexico.
Form No. 3197 © 1991 Jacobs Vehicle Equipment Company Printed in US.A. est
