Assembly - TM-55-1930-208-240261

TM 55-1930-208-24

4-10. HEAD, CYLINDER- Continued.

e. Assembly - Continued.

(29) Grind the inserts as follows:

(a) First apply the 31grinding wheel on the valve seat insert.

(b) Use the 60grinding wheel to open the throat of the insert.

shown in figure 3-95. The 31 face of the insert may be adjusted relative to the center of the valve face

with the 15and 60grinding wheels.

NOTE

Do not permit the grinding wheel to contact the cylinder head when grinding the insert.

When an insert has been ground to the extent that the grinding wheel will contact the

cylinder head, install a new insert.

(d) The maximum amount the exhaust valve should protrude beyond the cylinder head (when the valve is

closed) and still maintain the proper piston-to-valve clearance is shown in figure 3-95. Grinding will

reduce the thickness of the valve seat insert and cause the valve to recede into the cylinder head. If,

after several grinding operations, the valve recedes beyond the specified limits, replace the valve seat

insert.

(e) After grinding has been completed, clean t e valve seat insert thoroughly with fuel oil (item 9, Appendix

C) and dry the insert.

(f) After the valve seat insert has been ground, determine the position of the contact area between the valve

and the valve seat insert as follows:

(1) Apply a light coat of Prussian blue, or a similar paste, to the valve seat insert.

(2) Lower the stem of the valve in the valve guide and "bounce" the valve on the seat. Do not rotate the

valve. This procedure will show the area of contact on the valve face. The most desirable area of

contact is at the center of the valve face.

NOTE

The use of valve lapping compounds is not recommended.

(g) After the valve seat inserts have been ground and checked, clean the cylinder head before installing the

valves.

4-28