Piston Rings-Install - Pontiac tempest 1968 Service Manual

SIX C Y L I N D E R E N G I N E 6-31
J - 9 5 1 0
Fig. 6 - 6 1 Piston Pin Replacement
(see CONNECTING ROD AND PISTON ASSEMBLY -
R E M O V E AND R E P L A C E in this section),
2. Remove piston rings using J 8021.
3. Clean carbon, varnish, and gum from piston
surfaces, including underside 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
serviceable. Fit of bearings should be checked when
engine i s being assembled.
, .
Fig. 6-62 Checking Ring G a p
6. Inspect cylinder bores for out-of- round or ex­
cessive taper. See CYLINDER B O R E S - I N S P E C T .
PISTON RINGS—INSTALL
Two compression rings and one 3-piece oil control
ring, all above piston pin, are used on pistons for
both standard and premium fuel engines. The com­
pression rings are taper faced and also have either
a step or a chamfer on the inside diameter of the
bottom side. The top compression ring is molyb­
denum filled, which results in the center section of
the ring sealing edge appearing porous or grainy.
The lower compression ring is lubrite finished
(black).
Always install compression rings with the stamped
markings toward the top of the piston.
New rings are serviced for the standard size
pistons, and for .005", .010", .020", and .030" over­
size pistons. When selecting rings be sure they
match size of piston on which they are to be in­
stalled, 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 rings as follows:
1. Check pistons to see ring grooves and oil return
holes have been properly cleaned.
2. Place ring down at bottom of ring traveled part
of 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. 6-62). Gaps should be as follows:
Compression Rings .005-.025
Oil Ring .005-.055
. L t L M L
Fig. 6-63 Checking Ring Side Clearance