ARMY TM 9-6115-464-34
AIR FORCE TO 35C2-3-445-2
NAVY NAVFAC P-8-624-34
(13) Perform magnetic particle inspection in accordance with established procedures.
(14) Inspect valve seats of cylinder head. If they are pitted or if new valve guides were installed, the valve
seats must be refinished, using a tool with a 3/8 inch pilot. Both intake and exhaust valve seats
should be refinished on an angle of 30 degrees for intake valves and 45 degrees for exhaust valves.
Use a vibrating angle grinder type tool. The large diameter and surface area of the
valve seats makes obtaining a proper finish with a reamer type tool extremely difficult.
(15) Inspect valves for bent or broken stems, cracks, and pitting of sealing surface. Using a micrometer,
check valve stem diameter to determine wear. Stem diameter of intake valves shall be 0.3725 to
0.3735 inch. Stem diameter of exhaust valves shall be 0.3740 to 0.3750 inch.
(16) Check all threads for crossing, stripping, and peening. Repair minor thread damage with a thread
(17) Repair slightly damaged valves as follows:
(a) Polish stems with crocus cloth to remove minor nicks and scratches.
(b) Reface slightly pitted valves on a valve grinding machine. See table 1-1 for valve seat width.
(18) If valves and valve seats have been refinished or if contact surfaces are only slightly pitted, lap each
valve into its seat as follows:
(a) Install a light coil spring with enough tension to hold valve off its seat.
(b) Lubricate valve stem and guide.
(c) Apply a thin coating of coarse grinding compound to the valve face.
(d) Insert valve into valve guide and attach a hand grinding tool.
Avoid continuous round and round motion which could cut grooves in valve face and
seat. Failure to observe this caution could result in equipment damage.
(e) Rotate valve back and forth while applying firm pressure on the grinding tool.
(f) Release pressure on grinding tool, allowing coil spring to lift valve from its seat.
(9) Rotate valve 15° to 20° and repeat the grinding process,
(h) Periodically clean valve and seat to check progress.
(i) Replenish grinding compound and continue grinding until the valve seat and valve surfaces are in
(j) Remove valve. Clean valve and valve seat to remove all traces of coarse grinding compound.
(k) Apply a thin coating of fine grinding compound to face of valve.
(1) Install valve into cylinder head and repeat grinding process until a bright, silver-like band of uniform
width appears on both valve and seat.
(m) Remove valve. Clean valve and valve seat to remove all traces of grinding compound. Dry valve
and valve seat thoroughly.