TM 5-4320-302-146-16.PISTON ASSEMBLY (CONT)Location/ItemActionRemarksPiston rings for the correspondingly sized pistons andcylinders are also available in normal and two oversizes:PISTON RINGFIRST TRAPEZOIDALSECOND TAPER PISTONTHIRD OIL CONTROL(outside diam-RINGRINGRINGeter x insideDIMENSIONSDIMENSIONSDIMENSIONSdiameter xinchesinchesincheswidth)(millimeters)(millimeters)(millimeters)3.9370 x 3.5984 x3.9370 x 3.5984 x3.9370 x 3.5787 xNormal0.11810.09840.1969(100.0 x 91.4 x 3.0)(100.0 x 91.4 x 2.5)(100.0 x 90.9 x 5.0)3.9567 x 3.6181 x3.9567 x 3.6181 x3.9567 x 3.5984 xFirst oversize0.11810.09840.1969(100.5 x 91.9 x 3)(100.5 x 91.9 x 2.5)(100.5 x 91.4 x 5.0)3.9764 x 3.6378 x3.9764 x 3.6378 x3.9764 x 3.6181 xSecond oversize0.11810.09840.1969(101.0 x 92.4 x 3.0)(101.0 x 92.4 x 2.5)(101.0 x 91.9 x 5.0)REPLACEMENT OFPISTON, PISTON PIN,PISTON RINGS, ORCYLINDERSCAUTIONPistons, piston rings, and cylinders must always be matched to the samesize or oversize. Failure to match all three in size could cause seriousdamage to the engine.19. PistonReplace piston if tin plate or ring grooves areexcessively worn or damaged, ring lands aredamaged, piston is heavily scored or cracked, orpiston shows signs of excessive overheating.Replace piston if skirt diameter or out-of-round isnot within tolerance. If piston ring side clearanceexceeds the limit, replace piston. If piston pin boreis not within tolerance or is out-of-round, replacepiston.6-119
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