TM-9-2815-202-34 Technical Manual for 8V71T Engines for M109 Howitzer Download
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TM9-2815-202-34 (d) After grinding is completed, clean valve seat insert thoroughly. Measure concentricity of insert in relation to valve guide. If runout exceeds 0.002 inch, check for bent or worn valve guide before regrinding insert. (e) Determine position of contact area between valve and valve seat insert as follows: 1. Apply a light coat of Prussian blue or equivalent to valve seat insert. 2. Lower stem of valve in valve guide and bounce valve on seat. Do not rotate valve. 3. Remove valve and observe area of contact on valve face. Most desirable area of contact is at center of valve face. (7) Exhaust valves and springs (a) (b) (c) Insure valve stems are free from scratches or scuff marks. Valve faces must be free of ridges, cracks, or pitting. Replace valves if warped, excessively worn, or pitted. Using spring tester (87), replace valve spring (28) when a load of less than 25 Ibs will compress it to 1.80 inches. CAUTION Replace both springs under an exhaust valve bridge together. Mating a new spring with a used spring can cause unbalanced valve operation. (8) Cam followers and cam follower springs. (a) Examine cam follower springs (24) for wear or damage. Using spring tester (87), check spring load. Replace spring when a load of less than 172 Ibs will compress it to a length of 2.125 inches. 4-197