Cleaning and Inspection - TM-5-4320-273-140121

TM 5-4320-273-14

there is evidence of warping or deep pits. A good

valve spring seat locks (9) and valve stem cap (10).

method of detecting warping is to check each valve

(3) Release the valve spring compressor and

stem in a valve face grinder, and slowly rotate the

remove valve spring seat (11), valve spring (12), and

valve while the grinding wheel is brought near the

valve (3).

rotating valve face.

(4) Remove the valve tappets (14) from the crank-

(2) Using a valve face grinder, reface the valves

case. Do not remove valve guides (15) and valve seat

inserts (16) unless they are damaged.

to an angle of 45 degrees. Replace any valve that

measures less than 0.0625 inch (0.355 cm) from the

c. Cleaning and Inspection,

WARNING

top of head to the edge of the refaced outer circle.

(3) Install a pilot in the valve stem bore of the

DRY CLEANING SOLVENT, P-D-680

cylinder block. Set the stone on the valve reseating

or P-S 661, used to clean parts is

machine to the angle of 45 degrees and dress the

potentially dangerous to personnel

stone with the dresser. Place the grinder and stone

and property. Avoid repeated and

assembly over the pilot in the valve stem bore, and

prolonged skin contact. DO NOT use

grind inserts just enough to make a smooth seat.

near open flame or excessive heat.

(4) After grinding, valves and inserts should be

Flash point of solvent is 100 to 138F

lapped with a suitable lapping compound or they will

(38 to 60C).

leak due to improper seating within the first few

(1) Clean the top of the cylinder block with a

hours of operation.

scraper and cloth dampened in cleaning solvent (fed.

(5) Apply lapping compound to the valve face

spec. P-D-680), Clean all dirt and deposits from the

and put the valves back into their guides. Lap the

cooling fins with a scraper or putty knife.

valves by rotating them back and forth with a

(2) Clean all other parts with cleaning solvent;

reciprocating advancing tool.

dry thoroughly.

(6) Occasionally lift the valves and reseat them

(3) Inspect the cylinder block for cracks, scored

in a different position to ensure a uniform seat which

or scratched cylinder walls, or other damage. Replace

will show entirely around the valves, After valves

the block if damage cannot be corrected.

have been lapped in evenly, remove them from the

(4) Check the cylinder bores for wear. Measure

block and clean the valves and block.

the cylinder bores with an inside micrometer.

(7) When the grinding is completed, check the

Measure the bore lengthwise and crosswise above the

seat for concentricity, using a dial indicator.

ring travels; repeat the measurement at the top of

(8) With the valve stems inserted in the guide,

t h e cylinder bore. T h e difference in these

the stems shall have a clearance of 0.0025 to 0.0045

measurements will determine the amount of wear in

inch (0.006 to 0.011 cm). When the clearance becomes

the cylinder bore, the taper, and the out-of-round

0.008 inch (0.02 cm), you should replace the guides by

condition. If cylinder bores are worn more than 0.005

pressing them out with a driver that is slightly

inch (0.012 cm), rebore the cylinder with conventional

smaller than the external diameter of the guide. The

reboring equipment and hone until the bores are not

driver is also used to press in the new valve guides.

more than 0.001-inch (0.002-cm) out-of-round and are

not tapered more than 0.001 inch (0.002 cm). Nor-

e. Reassembly and Installation.

mally reboring to a 0.020-inch (0.05-cm) oversize is

(1) Install valve tappets (14, fig. 6-11) in the

sufficient. Maximum allowable oversize is 0.040 inch

engine block.

(0.1 cm).

(2) Place the valve springs (12) in their respective

(5) Clean the valves with a wire wheel brush to

valve chambers.

remove carbon from the valve faces and gum deposits

(3) Insert the valves (13) into the same bores from

from the stems. Wash the springs with cleaning

which they were removed. Assemble the valve stem

solvent (fed. spec. P-D-680); dry thoroughly.

cap (10) and valve spring seat (11) on the valve.

(6) Clean the valve seat insert and the top of the

(4) Using a valve spring compressor, compress

cylinder block. Inspect the valve-seat inserts for

the valve spring and install valve spring seat locks

looseness and excessive wear replace as necessary.

(9).

(7) Inspect the valve springs for breaks and wear.

(5) Position gasket (4) on crankcase and install

Compare with a new spring and replace if weak or

cylinder block assembly (3). Secure cylinder block

damaged.

assembly to crankcase with Lockwasher (2) and nut

(l).

(8) Inspect the valves for burned, pitted, or crack-

ed faces; replace if defective or if grinding is not

NOTE

plausible.

Tight.en cylinder block mounting nuts to 62 to 78 foot-

pounds (8.57 to 10.78 kg-m) torque.

d. Valve and Valve Seat Refacing.

(1) Replace valves and valve seats only when

(6) With the tappets in their lowest position on

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