Piston Fitting (8-Cylinder); Piston Rings (8-Cylinder) - Jeep 1979 CJ-5 Technical & Service Manual

ENGINES 1B-61
The pistons are cam-ground and are not perfectly
round. The ring belt area contains three piston rings,
two compression rings, and one oil control ring above
the piston pin.
The piston pin boss is offset from the piston centerline
to place it nearer the thrust side of the piston, min-
imizing piston slap.
To ensure correct installation of the pistons in the
bore, two notches are cast in the top perimeter of the
piston on 304 (5 liter) and 360 (6 liter) CID engines. The
notches must face forward (fig. 1B-95).
8 0 0 5 0
Ftg
I M S
Piston Assembly Into Bore
Piston Fitting
Micrometer Method
(1) Use inside micrometer to measure cylinder bore
inside diameter a t point 2 5/16 inch (59 mm) below top
of bore crosswise to block.
(2) Measure outside diameter of piston.
NOTE: Pistons are cam ground and must be measured
at right angle to piston pin at centerline of pin (fig. 1B-
97).
(3) Difference between cylinder bore diameter and
piston diameter dimension is piston-to-bore clearance.
Feeler Gauge Method
(1) Remove rings from piston.
(2) Insert long 0.0005-inch (0.013 mm) feeler gauge
into bore.
(3) Insert piston (top first) into bore alongside
feeler gauge. With entire piston inserted in bore, piston
should not bind against feeler gauge.
(4) Repeat steps (2) and (3) with long 0.002-inch
(0.051 mm) feeler gauge. Piston should bind.
If piston binds on the 0.0005-inch (0.013 mm) gauge,
piston is too large or bore is too small. If piston does not
bind on the 0.002-inch (0.051 mm) gauge, piston may be
enlarged by knurling or shot-peening. Replace pistons
that are 0.004-inch (0.102 mm) or more undersize.
3.629 in.
(92.1766mm)
1T624 in.
(92.0496mm)
3.680 in.
(93.477mm)
~ 6 7 0 in.
(93.218mm)
3.333 in.
(84.6582mm)
3.328 in.
(84.5312mm)
3.339 in.
(84.8106mm)
3.329 in.
(84.5566mm)
D I A M E T E R
1ST A N D
2 N D
G R O O V E
D I A M E T E R
3 R D
G R O O V E
D I A M E T E R
1ST A N D
2 N D
G R O O V E
D I A M E T E R
3 R D
G R O O V E
360 CID
LL
> 304 CID
.0805 in.
(2.0447mm)
.0795 in.
(2.0193mm)
1?
MEASURE PISTON
A T T H I S A R E A
FOR F I T T I N G
.1895 in.
'(4.8133mm)
.1880 in.
(4.7752mm)
GROOVE
H E I G H T
4 1 9 0 9
Fig. 1B-97 Piston Measurements
Piston Rings
The top compression ring is made of moly-filled iron.
The second compression ring is made of cast-iron. The
oil control is a three-piece steel design.
Ring Fitting
(1) Clean carbon from all ring grooves. Be sure oil
drain openings in oil ring grooves and pin boss are open.
CAUTION: Do not remove metal from grooves or
lands. This will change ring groove clearances and will
damage ring-to-land seating.
(2) Check ring side clearance with feeler gauge fit-
ted snugly between ring land and ring. Roll ring around
groove in which it is to operate. It must fit freely at all
points (fig. 1B-97). Refer to Specifications for correct
ring side clearance.