TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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Figure 6-63. (2) Valve seats. Replace cylinder assembly which do not show perfect contact with valve (41, fig. B-4) when inserts do not fit securely in face. Grind inserts (fig. 6-63) as described in (a) the cylinder. Grind seats which do not show through (e), below. perfect contact with valve face. Grind seats (a) A 45 degree angle grinding stone must c. Honing Specifications. (Part No. be used to grind valve seat inserts. (b) Dress seat on the insert with stone, using valve seat grinding machine. (c) After dressing seat of insert, check valve contact as described in paragraph 6-31b. (d) When perfect contact is obtained, narrow seat on insert to width specified in figure 6-63 by grinding inner wall and exposed face of insert to the angles specified. (e) Keep valve seat area as near as possible to center of valve face. Valves should never seat at the top or bottom of the valve face area. b. Cylinder Bore. Replace cylinder assembly when joint between cylinder head and cylinder barrel is pitted or eroded. Replace cylinder assembly when cylinder bore dimensions are not within limits specified in the overhaul standards (table 6-15), or when average dome end measurement is larger than average flange end measurement. Reanodize head if required. Hone cylinder to remove scratches, scoring or ring ridge. Hone cylinder when out-of-round more than 0.003 in. Hone cylinders as described in c and d, below. 10865297, FSN 2815-765-9711 cylinder only) (1) Cross hatch angle to be 35 degrees off the horizontal. (2) Cross hatch to be cut uniformly in both directions. (3) Cross hatch to be clean-cut, but not sharp, and free from torn or folded metal. (4) The micro-finish roughness should average between 35 and 45 micro-inches, rms (root mean square deviation from the mean), as measured on the profilometer machine (Micrometrical Mfg. Company, Ann Arbor, Michigan, Type QA, Type V Moto-Trace or equivalent). (5) The plateau area should be 1 / 2 to 2 / 3 of the surface area. (6) The plateau should be free from bur- nished or glazed surface. (7) The surface is to be free of imbedded particles. d. Honing Recommendations. (Part No. 10865297, FSN 2815-765-9711 cylinder only) (1) Honing stones should be Army Nos. 11662775-1 and 11662775-2 used alternately around the honing head. The stones are ap- 6-70