reseat in a different position to insure uniform
seating. After valves are properly lapped, remove
(1) Remove the cylinder block (para 3-24).
them from cylinder block and wash valves and
(2) Refer to figure 3-28 and remove the engine
block thoroughly in an approved cleaning solvent
( F E D - P D - 6 8 0 ) . Tag each lapped valve with its
(3) Remove valve guides and seats as shown
mated valve guide for proper assembly.
by step 1 and 2 figure 3-29.
(4) Inspect the valve springs (9) for damage
c. Disassembly. Refer to figure 3-30 and
and test for spring tension as follows:
disassemble the valves and attaching parts.
(a) Test tension of spring with a suitable
spring tension tester.
(1) Clean the valve guide parts in the cylinder
(b) Compress each spring to 1.271 inches
blocks and blow out with compressed air.
and note reading on the tester. If reading is less
(2) Clean the valve seat insert recesses and the
than 51 pounds, replace spring.
top of cylinder block.
f. Reassembly. R e f e r t o f i g u r e 3 - 3 0 a n d
e. Inspection and Repair.
reassemble the valves and attaching parts in reverse
(1) Inspect the valves (7, fig. 3-30) and seats
procedure of removal.
for burned, pitted, or cracked faces.
(2) The cylinder blocks have replaceable valve
guides. The valve stems should have a clearance of
Make certain valve spring seat locks (6)
0.0025 to 0.0045 inch in the guides. Replace valve
guides that exceed 0.008 inch clearance.
s p r i n g tension.
( 3 ) Grind serviceable valves (7) and seat
inserts (10) to an angle of 45 degrees to the vertical
(1) Install valve guides and seats as shown in
steps 3, 4, and 5 figure 3-29.
center lines. After grinding, lap the valve and valve
(2) Refer to figure 3-28 and install the valves
seat insert with suitable lapping compound, to
in reverse procedure of removal.
provide proper fit. C l e a n the valve and apply
lapping compound to the valve face. Insert the
(3) Install the cylinder block (para 3-24).
h. Adjustment. Adjust the valve tappets (TM 5-
valve in their valve guide (11) and lap by rotating
t h e valve back and forth with a reciprocating
advancing valve tool. Occasionally lift the valve