SIX
CYLINDER ENGINE
6-31
J-9510
Fig.
6-61
Piston
Pin
Replacement
(see
CONNECTING
ROD AND
PISTON
ASSEMBLY
-
REMOVE
AND
REPLACE
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
is being assembled.
,
.
Fig.
6-62
Checking Ring
Gap
6. Inspect cylinder bores for
out-of-
round
or ex-
cessive taper. See
CYLINDER BORES-INSPECT.
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
.
LtL ML
Fig.
6-63
Checking Ring Side Clearance
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