User Manual

Page 5-14
200 BENCH PROCEDURES
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.
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.
Special Tools Required
앫 Piston Ring Expander PT6587
앫 Keystone Ring Groove Gauge J 29510
Disassembly
Refer to Figure 5-11.
1. Using piston ring expander PT6587, remove
piston rings.
Figure 5-11 — Piston Ring Removal
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.
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.
5-101.bk Page 14 Friday, March 17, 2006 11:05 AM