5-101.bk Page 14 Friday, March 17, 2006 11:05 AM The two-piece piston design incorporates two compression ring grooves and one oil ring groove. A plasma-faced, keystone-type ring is used in the top ring location. A tapered chrome, rectangular-type ring is used in the second ring groove. The oil control ring is located in the third (or lower) groove, nearest the piston pin bore. New piston rings are designed to further improve oil control, especially relating to particulates control. Disassembly Refer to Figure 5-11. 1. Using piston ring expander PT6587, remove piston rings. E7 piston crowns have been modified in the oil control ring groove area.
During the second quarter of 1996, the oil drainback holes have been eliminated and replaced by an oil accumulator relief. The relief is machined into the lower half of the third ring land face, 360 degrees around the piston circumference. Current E7 pistons are NOT interchangeable with 1989/1990 E7 pistons. Figure 5-11 — Piston Ring Removal Special Tools Required 2. Thoroughly clean ring grooves and combustion bowl area. All carbon must be removed. Carbon left in grooves will reduce ring clearance and prevent replacement rings from seating properly. Piston Ring Expander PT6587 Keystone Ring Groove Gauge J 29510 Be sure that cleaning solvent is approved for steel/aluminum.
Incompatible solvent may cause damage to pistons or skirts. 3. Clean pistons with approved solution and a brass brush. Take care to avoid damaging pistons while cleaning. Page 5-14 200 BENCH PROCEDURES