Piston Rings; Installing Piston Pin - Pontiac Grand Prix Service Manual

INGINE
6-69
3. Coat piston pin and rod lightly with graphite
lubricant.
4. Place tool J 6901-3 in piston pin and press pin into
piston and connecting rod (Fig. 6-123) until piston pin
bottoms against plunger of tool J 6901. Piston must
turn freely on pin. If piston binds on pin, disassemble,
hone piston pin bosses slightly and reassemble.
PISTON RINGS
REMOVE
1. Remove piston and rod assembly. See CONNECT-
ING ROD AND PISTON ASSEMBLY
-
REMOVE
AND REPLACE.
2. Remove piston rings using J 7 1 17 or J 802 1.
3. Clean carbon, varnish, and gum from piston
surfaces, including under side of piston head. Clean
ring grooves, and oil holes in oil ring groove, using
suitable cleaning tools and solvent.
4. Carefully examine piston for rough or scored
bearing surfaces; cracks in skirt or head; cracked,
broken, or worn ring lands; scored, galled, or worn
piston bosses. Damaged or faulty pistons should be
replaced.
5. Inspect bearing shells to see that they are service-
able. Fit of bearings should be checked when engine is
being assembled.
6. Inspect cylinder bores for out-of-round or excessive
taper. See CYLINDER BORES-INSPECT.
PISTON RING CHECK AND INSTALL ON PIS-
TON
Two compression rings and one 3-piece oil control
ring, all above the piston pin, are used on pistons for
both standard and premium fuel engines. The compres-
sion rings are taper faced and also have either a step
or chamfer on the inside diameter of the bottom side.
The top compression ring is molybdenum filled, which
results in the center section of ring sealing edge
appearing porous or grainy. The lower compression
ring varies depending upon the engine. See specifica-
tions at the end of this section.
Regardless of engine type, always install compression
rings with the stamped markings toward the top of
piston.
New rings are serviced for the standard size pistons,
and for. 005", .010", .020", and .0301' oversize pistons.
When selecting rings, be sure they match the size of
the piston on which they are to be installed, i.e.,
standard rings for standard pistons, .010" oversize
rings for .010" oversize pistons, etc. Ring gap and side
clearance should be checked while installing as
follows:
1. Check pistons to see that ring grooves and oil return
holes have been properly cleaned,
2. Place ring down at the bottom of the ring traveled
part of the cylinder bore in which it will be used.
Square ring in bore by pushing it into position with
head of piston.
3. Measure gap between ends of ring with feeler gauge
(Fig. 6-124). Gaps should be as follows:
Compression Ring .0 10"-.030"
Fig. 6-123 Installing Piston Pin
Fig. 6-124 Checking Ring Gap