Figure 4-8. Indicating Valve Seat

TM 10-3930-644-14&P

Figure 4-10. Checking Valve Face in "V" Blocks

lightly with Prussian blue and drop the valve into

Figure 4-8. Indicating Valve Seat

position, oscillating it slightly to transfer the blue

pattern to the valve face. This should show a

4. Valves

contact width of .0625" to .0938", and should fall

well within the width of the valve face, leaving at

Inspect valves for condition and replace any that are

least .0625" on either side where the blue does

"necked", cracked or burned, also any on which valve

not show. If the contact is over .0938" wide, the

stems are bent or worn more than .002" over the

seat in the head may be narrowed by using a

maximum allowable limits. Reface or replace all valves.

150 stone to reduce the outside diameter, or

using a 600 or 750 stone to increase the inside

diameter (Figure 4-11 and 4-12).

Figure 4-9. Allowable Head Thickness of Refaced

Valves

Figure 4-11. Method of Narrowing Valve Seats

Replace all valves having less than 50% margin

thickness (outer edge of valve head) after refacing has

been completed. To check this dimension, compare the

refaced valve with a new valve (Figure 4-9).

Check all refaced or new valves in Y-blocks with

indicator (Figure 4-10) to determine if the contact face is

true with the stem within .002". If not, repeat the

refacing operation.

After the valves and seats have been refaced and

reground. coat the seat

Figure 4-12. Valve Position in Cylinder Block

R-104-1

3-10