Valve Guides - TM-10-3930-644-14-P0173

TM 10-3930-644-14&P

Carefully inspect the crankcase for cracks around the

Replace worn guides as required by using a suitable

exhaust valve areas.

driver and an arbor press from the combustion side to

the correct depth below the valve seat. Refer to Figure

Inspect spring coils for bright spots that may be an

4-3 and TOPIC 1. FITS AND TOLERANCES.

indication of spring weakness when found beyond the

closely spaced dampening coils at the spring ends.

Over-speeding the engine can cause this condition.

Replace any rusted, weak, cracked or broken springs.

Check the tension of each valve spring with a spring

scale designed for the purpose. Refer to following

subparagraph 5. Valve Springs.

1. Valve Guides

Clean the valve stem guides, removing lacquer

or other deposits by running a valve guide

cleaner or wire brush through the guides.

Check guides for wear by using a "Go and No-

Go" plug gage, or a telescope gage and a 1"

micrometer. Replace all guides that are worn

Figure 4-3. Distance from Block Face to Top of Valve

bell-mouthed and have increased .0015" in

Guide

diameter.

Refer to TOPIC 1.

FITS AND

TOLERANCES

for

maximum

diameter

CAUTION

permissible, to determine actual amount the

When replacing guides that are ferrox

diameter has increased.

When necessary,

coated, do not ream, since these are

remove all valve guides; use an arbor press and

all pre-reamed before being ferrox

press them out from the combustion chamber

coated any further reaming will

side with a driver slightly smaller than the O.D.

remove the coating.

of the valve guide.

2. Valve Seat Inserts

Valve guides are a press fit, and service guides

are especially machined to press in place and

The exhaust valve seat insert is held in place by

give correct stem clearance without further

a shrink fit.

machining. However, the valve seat MUST be

re-cut concentric with the new guide whenever

new guides are installed.

Figure 4-4. Removing Exhaust Valve Seat Insert

Figure 4-2. Removing Valve Guides

R-104-1

3-8