Cleaning, Inspection, and Repair. - TM-5-4320-258-340041

TM 5-4320-258-34

(4) Lift each valve from the top of the

block. Place valves in order in a rack to assure that

each will be reassembled in the same valve guide from

which it was removed.

(5) Remove the valve rotators (3 or 8),

spring retainers (4 or 9), and valve springs (5 or 10).

Remove the valve tappet assemblies (13).

(6) Do not remove the valve guides (11) or

valve seat inserts (12) unless inspection indicates that

they are faulty.

c. Cleaning, Inspection, and Repair.

(1) Clean the valves, valve springs, and

valve tappet assemblies with cleaning solvent (FED.

Spec. P-D-680); dry thoroughly. Remove carbon

deposits with a wire brush.

(2) Clean the valve guides installed in the

block with a valve guide cleaner or wire brush. Remove

all lacquer and other deposits.

(3) Clean the valve seats with a wire brush.

(4) Inspect the valves for cracks, bent

stems, distortion, and wear (table 4-1). If the valves are

not seriously damaged, regrind them. After grinding, the

valve head thickness must be at least 50 percent the

thickness of a new valve. Replace the valves if they are

Figure 4-4. Valve guide installation dimensions.

ground to less than this amount. Check the reground

valves on V-blocks with an indicator. The contact face

(7) Check the exhaust valve seat inserts

must be true with the stem to within 0.002 inch.

for cracks or loose mounting. Pull out faulty valve seat

(5) Check for loose or worn valve guides.

inserts. Replace original valve seats with new 0.010-

Check the internal diameter of the valve guide with a

inch oversized valve seats. Counterbore the original

telescope gage and a micrometer. Replace guides that

valve seats to a diameter of 1.3535 to 1.3545 inches.

are worn to a bell-mouthed shape or guides that have a

This will provide the required press fit. If valve seats

maximum diameter of more than 0.3447 inch.

have been counterbored previously, rebore to 0.01 inch

Caution: Do not attempt to ream the valve

oversize to provide an 0.003- to 0.005-inch press fit.

guides after seating them. Guides are pre reamed

Counterbore deeply enough so that the boring tool will

and coated.

Further reaming will remove the

clean up the bottom of the bore to assure proper heat

coating.

conduction from the valve insert. Chill the valve seats

(6) If the valve guides are worn or

in dry ice for 20 minutes. Install the valve seat in place

damaged, press out the guides from the combustion

with a piloted driver, using an arbor press or by applying

side, using a driver that is slightly smaller than the

light blows with a hammer until the valve seat is resting

external diameter of the guide. With the driver, press in

against the bottom of the bore. Roll or peen the valve

new guides from the combustion side. When properly

seat in place.

seated, valve guide tops will be 1 13 / 32 inches from

(8) Check the valve springs for cracks and

the top of the block (fig. 4-4).

distortion.

Intake and exhaust valve springs are

identical. Test compression strength with a spring

tester. Compression strength must be as follows:

4-8