Valve Mechanism, Cleaning, Inspection and Repair

TM 10-3930-630-34

11-4.

Valve Mechanism, Cleaning, Inspection and

Repair

a. Clean parts in cleaning solvent (Fed. Spec. P-

D-680) and dry thoroughly.

b. Remove all carbon and burned oil from valves.

c. Check valves and seats for excessive burning,

cracks and pitting.

d. Check valve guides by inserting valves and

noting amount of side play.

e. Check intake valves as follows:

(1) Stem diameter must be 0.3414 to 0.3406

inch (8.67 to 8.65 mm).

(2) Minimum diameter wear limit is 0.3386

inch (8.60 mm).

(3) Stem clearance limits in valve guide must

be 0.0026 to 0.0008 inch (0.066 to 0.020 mm).

(4) Maximum clearance is 0.0046 inch (0.116

mm).

(5) Desired clearance is 0.0015 inch (0.038

mm).

f. Check exhaust valves as follows:

(1) Stem diameter must be 0.3385 to 0.3377

inch (8.59 to 8.57 mm).

Figure 11-3. Valve guide removal.

(2) Minimum diameter wear limit is 0.3357

inch (8.52 mm).

(3) Stem clearance limits in valve guide must

be 0.0055 to 0.0037 inch (0.139 to 0.093 mm).

(4) Maximum clearance is 0.0075 inch (0.190

mm).

(5) Desired clearance is 0.0045 inch (0.114

mm).

g. Replace valves that do not comply with the

above tolerances.

h. Inspect and repair valve seats as follows:

(1) Inspect valve seats for cracks and

damage.

(2) Check all inserts for cracks and damage

and for looseness in mounting.

(3) Measure outside diameter of exhaust

valve insert.

(4) Clean and counterbore the block for a

0.010 inch (0.254 mm) large insert. When machining

counterbore, go deep enough to provide full contact of

the insert.

(5) Figure 11-5 shows standard insert and

counterbore dimensions.

Figure 11-4. Valve seat removal.

(6) Always use an oversize insert as a

replacement.

(7) Insert must be a press fit. Place insert in

a container of dry ice before installing. Use gloves to

remove from ice and install insert to prevent freezing or

burning hands from dry ice.

11-3