Pistons; Feeler Gauge Method; Ring Fitting; Micrometer Method - Jeep J-10 Series 1982 Technical & Service Manual

1B-54 ENGINES
CAUTION: Use care when rotating the crankshaft
with bearing caps removed. Eiisure the connecting rod
bolts do not accidentally come in contact with the rod
journals and scratch the surface. Bearing failure would
result. Short pieces of rubber hose slipped over the con
necting rod bolts will provide protection during
installation.
(2) Install bearing inserts, cap and retaining nuts.
Tighten with 33 foot-pounds (45 N#m) torque.
(3) Install oil pan using replacement gaskets and
seals. Tighten drain plug.
(4) Fill crankcase with clean oil to specified level.
PISTONS
Aluminum alloy Autothermic pistons are used. Steel
reinforcements provide strength and control expansion.
The ring land area above the piston pin provides for two
compression rings and one oil control ring.
The piston pin boss is offset from the centerline of the
piston to place it nearer the thrust side of the piston,
minimizing piston slap.
An arrow on the top surface of the piston indicates the
correct installation position in the bore. The arrow
points toward the front of engine when installed cor
rectly (fig. 1B-82).
ARROW POINTS
TO FRONT
41908
Fig. 1B-82 Pistons Correctly Positioned In Cylinders
Piston Fitting
Micrometer Method
(1) Measure inside diameter of cylinder bore 2-5/16
inches (58.725 mm) below top of cylinder.
(2) Measure outside diameter of piston.
NOTE: Pistons are cam ground and must be measured
at a right angle (90°) to piston pin at centerline of pin
(fig. 1B-88).
(3) Difference between cylinder bore diameter and
piston diameter is piston-to-bore clearance.
3.333 in.
(84.6502mm)
3.328 in.
(84.5312mm)
3.339 in.
(84.8106mm)
3.329 in.
(84.5566mm)
DIAMETER
1ST AND
2ND
GROOVE
DIAMETER
3RD
GROOVE
r \
^ ^
&
0.0805 in.
(2.0447mm)
0.0795 in.
(2.0193mm)
0.1895 in.
(4.8133mm)
0.188 in.
(4.7752mm^
MEASURE PISTON
AT THIS AREA
FOR FITTING
GROOVE
HEIGHT
41909
Fig. 1B-83 Piston Measurement
Feeler Gauge Method
(1) Remove rings from piston.
(2) Insert long 0.0005-inch (0.013 mm) feeler gauge
into cylinder 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) above with long 0.002-
inch (0.051 mm) feeler gauge. Piston should bind.
If piston binds on 0.0005-inch (0.013 mm) gauge, pis
ton is too large or bore is too small. If piston does not
bind on 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.
Piston Rings
The two compression rings are made of cast iron. The
oil control ring is a three-piece steel design.
Ring Fitting
(1) Clean carbon from all ring grooves. Oil drain
openings in oil ring grooves and pin boss must be open.
Do not remove metal from grooves or lands. This will
change ring groove clearances and will damage ring-to-
land seating.
(2) Measure ring side clearance with feeler gauge
fitted snugly between ring land and ring. Rotate ring in
groove. It must move freely at all points (fig. 1B-84).
Refer to Specifications for correct ring side clearance.
(3) Place ring in bore and push down with inverted
piston to position near lower end of ring travel. Measure
ring gap (joint clearance) with feeler gauge fitting
snugly in ring end gap (fig. 1B-85). Refer to Specifica
tions for correct ring gap clearance.