Valve Reconditioning Procedure
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ScribdTranslationsValve Reconditioning Procedure
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ScribdTranslationsVALVES RECONDITIONING PROCEDURE
1 the valve stem must be free of carbon the working head of the machine must be adjusted
to 30 to 45 degrees the abrasive stone is mounted and first adjusted to 90 degrees on the
graduated scale and a light pass is made over the valve face to eliminate irregularities
2, mount the valve in the working head and tighten the knurled sleeve to hold the stem
firmly. Press the valve firmly into the working head to center the tip of the stem in the
conical stop if necessary. You can adjust the stop in or out depending on the length of the
stem
3 Turn on the grinding machine and move the valve head across the wheel so that it is
aligned with the face of the grinding wheel.
4. Turn the grinding wheel until it barely touches the face of the abrasive wheel. Move the
valve back and forth across the face of the wheel and adjust the advance to have light
contact between the valve and the abrasive wheel.
5. The necessary metal must be removed to produce a smooth and concentric face. If the
edge or margin of the valve is too thin with the grinding, it must be changed because it will
overheat and burn if it is too thin.
6 The valve is removed from the working head and held in the attachment support to grind
the valve stem towards the cup wheel and proceed to only remove the necessary material to
eliminate the cavities and pitting in the tip of the stem
VALVE SEAT REPLACEMENT and conditioning
Valve seats should be replaced if they are cracked or if they become burned or eroded too
much to resurface. Damaged integral valve seats must be bulged to make room for the new
insert seat. Manufacturers of replacement valve seats supply tables that specify the
appropriate seat insert to be used. Exhaust valve seats operate at temperatures 100" to 150"
F (56" to 83" C) hotter than integral seats up to 900' F (480" C). Removable valve seats are
available in cast iron, stainless steel, nickel cobalt or powder metal
Valve seat rectification process
1 the valve guides and seats must be cleaned, this is important for correct centering so that
the seat is concentric with the guide
2 the expansion pilot must be inserted into the guide and check its correct placement
3 select the stone of the required diameter and angle and install it on the support
4 put the support and the stone on the grinding machine
5 once everything is installed, turn it with the drill and apply a slight precision and rectify
it. In the first rectification it is slight, only one side of the seat appears, you have to turn the
expansion pilot half a turn in the valve guide and make another light pass. This process the
seats must remain concentric with the guides
Checking the installed height
When the valves and/or valve seats have been machined, the valve projects farther than
before on the rocker arm side of the head. (The valve face is slightly recessed into the
combustion chamber side of the head.) Therefore, the valve spring tension is reduced
because the spring is not as compressed as originally. To restore the original valve spring
tension, special valve spring spacers or inserts are installed under the valve springs.
These shims are generally called valve spring inserts (VSI). Valve spring inserts are
generally available in three different thicknesses:
1. 0.015 inches (0.38 millimeters) for swing valve spring pressure 2. 0.030 inch (0.75
millimeters) generally, for new springs in cylinder heads that have had valve seats
ground and valves ground
3. 0.060 inches (1.5 millimeters) required to carry mounted height per specifications,
especially
Valve seals
Leakage beyond the valve guides is a major oil consumption problem in any overhead cam
(or overhead cam) engine. There is a high vacuum in the intake port.
Most engine manufacturers use valve seals on both the intake and exhaust valves. Two
basic types of valve stem seals are used. The umbrella valve stem seal attaches firmly to the
valve stem and moves up and down with the valve. Any oil that spills from the rocker arms
is diverted out over the valve guide, just as water is diverted over an umbrella.
The cylinder head can be assembled after the head has been thoroughly cleaned with soap
and water to remove all grit and metal shavings remaining from the valve grinding
operation. The valves are mounted in the head one at a time. Give the valve guide and stem
a liberal coat of engine oil, and install the valve into its guide. Install the umbrella or
positive valve stem seals. Push the umbrella seals down until they touch the valve guide.
Use a plastic sleeve over the valve tip when installing positive seals. Make sure the positive
seal is fully seated in the valve guide and is square. Hold the valve against the seat when
the valve spring seat or insert, valve