ARMY TM 9-2815-260-24 AIR FORCE TO 38G1-126-2 MARINE CORPS TM 09244A/09245A-24 5-81 NOTE Piston rings come pre-installed in new piston and liner assemblies.  Leave piston inside liner. (e) Install piston rings as follows: 1 Install oil ring expander in bottom ring groove of piston (4) using piston ring expander.  Position end gap of oil ring expander toward either side of piston pin. 2 Install oil control ring (7c.) in bottom ring groove over ring oil ring expander.   Position end gap of oil control ring on opposite side of piston from oil ring expander gap. 3 Identify top side of compression rings (7a. and 7b.).  Top side of rectangular and keystone compression rings are identified by depression marks on top side of two rings. 4 Install rectangular compression ring (7b.) in center ring groove of piston (4) with depression marks facing top of piston. 5 Position gap in rectangular compression ring (7b.) on opposite side of piston from gap in oil control ring (7c.). 6 Install keystone compression ring (7a.) in top ring groove of piston (4) with depression marks facing top of piston. 7 Position gap in keystone compression ring (7a.) on opposite side of piston from gap in rectangular compression ring. (f) Measure piston protrusion as follows: 1 Press down on top of piston (4) to remove oil clearances before measuring piston protrusion. 2 Position gauge on cylinder block.  Zero dial indicator against cylinder block. 3 Position gauge across piston.  While pressing gauge downward, rotate crankshaft until piston is at Top Dead Center (TDC) position. 4 Measure piston height at several positions around piston.  Piston Protrusion (above cylinder block deck) should be 0.003 - 0.012 in. (0.08 - 0.30 mm). (g) If piston protrusion is out of specifications, check dimensions of piston, cylinder block, crankshaft, and bearings to determine the cause.