TM 9-2320-272-24-4
5-25. CYLINDER HEAD REPAIR (Contd)
1.
Apply light coat of lapping compound to valve (2) and lap valve (2) to valve seat insert (1).
2.
Clean lapping compound from valve (2) and valve seat insert (1).
3.
Measure width of valve seat insert (1). Limits are 0.060-0.080 in. (1.52-2.03 mm). If beyond limits,
replace cylinder head (4).
4.
Check contact surface between valve (2) and valve seat insert (1) as follows:
a. Apply light coat of pigment to valve face (3).
b. Lower valve (2) into valve guide (5) and let valve (2) drop against valve seat insert (1).
NOTE
Do not rotate valve when pushing valve against valve seat insert.
c. Push up on valve stem (6) until valve face (3) is about 1 in. (25.4 cm) above valve seat insert (1).
d. While releasing valve stem (6), apply pressure to valve (2) until valve face (3) makes contact with
valve seat insert (1). Repeat several times to get good imprint on pigment.
NOTE
Do not smear pigment from valve.
e. Remove valve (2).
f. Imprint on pigment should have an even contact surface all around center of valve face (3). If
pigment imprint is uneven, mark valve (2) and valve seat insert (1) for grinding.
NOTE
Repeat step 4 for all valves to check contact surface between valve
and valve seat insert.
5.
Grind valve (2) and valve seat insert (1) if valve (2) is new or has an uneven contact surface.
a. Use a 30 grinding wheel on valve seat insert (1) for intake port (7).
b. Use a 45 grinding wheel on valve seat insert (1) for exhaust port (8).
NOTE
If contact surface is at bottom of valve face, valve seat insert will
require more grinding with 15 wheel.
c. To center contact surface on valve face (3), grind area (11) of valve seat insert (1) with a 60
wheel, and area (12) of valve seat insert (1) with a 15 wheel.
d. Using valve refacing machine, grind face of intake valve (2) to a 30 angle or a 45 angle for
exhaust valve.
6.
If valve stem tip (10) is not flat, dress tip for flatness on grinding wheel.
7.
Measure valve (2) depth from bottom of cylinder head (4) to surface when valve (2) is seated against
valve seat insert (1).
a. Position gauge block flat on surface of cylinder head (4) with plunger extended to cylinder head (4)
surface. Adjust dial indicator to zero.
b. Position gauge block flat on surface of cylinder head (4) with plunger extended to valve (2).
c. Valve (2) depth must measure 0.035-0.056 in. (0.89-1.42 mm) below bottom surface of cylinder
head (4).
d. If measurement is not within limits, use new valve (2) and repeat steps a through c.
e. If measure is beyond limit, replace cylinder head (4).
8.
Using pigment, check contact surface (9) between face of valve (2) and valve seat insert (1) (step 4d.).
9.
Clean cylinder head (4) and valves (2) after valves (2) and valve seat inserts (1) have been ground
(para. 2-14).
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