Pistons And Connecting Rods; Removing Piston Pin - Jeep J-10 Series 1982 Technical & Service Manual

PISTONS AND CONNECTING RODS
The pistons are lightweight, cast aluminum with slip
per skirt and cam ground so that the diameter across the
thrust face is larger than the diameter fore and aft of
the engine. Two compression rings and one oil control
ring are used. All are located above the piston pin.
The piston pins are offset toward the thrust side
(right-hand side) to provide a gradual change in thrust
pressure against the cylinder wall as the piston travels
within the cylinder. The piston pins are tempered steel
and have a floating fit in the pistons. They are retained
in the connecting rods by a press fit.
The connecting rods are made of Armasteel. Full pres
sure lubrication is directed to the connecting rods by
drilled oil passages from the adjacent main bearing jour
nal. Oil holes at the connecting rod journals are located
so that oil is supplied to give maximum lubrication just
prior to full bearing load.
Removal
(1) Remove cylinder head according to procedure
described in Cylinder Head Removal.
(2) Remove oil pan according to procedure described
in Oil Pan Removal.
(3) Remove ridge and/or deposits from upper end of
cylinder bores with ridge reamer tool. Before ridge or
deposits are removed, turn crankshaft until piston is at
bottom of stroke and place a cloth on top of piston to
collect cuttings. After ridge and/or deposits are re
moved, turn crankshaft until piston is at top of stroke
and remove cloth and cuttings.
(4) Inspect connecting rod and piston for cylinder
number identification and, if not identified, mark them.
(5) Remove bearing cap and install Connecting Rod
Bolt Guide Set J-6305-11.
(6) Carefully remove connecting rod and piston as
sembly by pushing out with knurled handle of long
guide.
Disassembly
CAUTION: Use care at all times when handling and
servicing connecting rods and pistons. To prevent pos
sible damage to these units, do not clamp rod or piston
in vise because they may become distorted. Do not allow
pistons to strike against one another, against hard ob
jects or bench surfaces because distortion ofpiston con
tour or nicks in the soft aluminum material may result.
(1) Remove piston rings using suitable piston ring
removal tool.
(2) Install guide bushing of Piston Pin Removal and
Installation Tool J-24086.
(3) Position piston and connecting rod assembly on
support and place assembly on arbor press (fig. 1B-30).
(4) Press pin out of connecting rod with Piston Pin
Removal Tool J-24086.
ENGINES 1B-19
Fig. 1B-30 Removing Piston Pin
(5) Remove assembly from press, remove piston pin
from support and remove tool from piston and rod.
(6) Clean carbon, varnish, and gum deposits from
piston surfaces, including underside of piston head.
Clean ring grooves and oil holes in oil ring groove with
appropriate cleaning toqls and solvent.
(7) Clean piston pin, rod, cap, bolts and nuts in
appropriate solvent. Reinstall cap on connecting rod to
prevent inadvertent mixing of caps and connecting rods.
(8) Carefully examine piston for rough or scored
surfaces; cracks in skirt or head; cracked, broken, or
worn ring lands; and scored, galled, or worn piston bos
ses. Damaged or defective pistons should be replaced.
(9) Inspect piston pin for scoring, roughness, or
uneven wear and proper fit.
(10) Inspect rod bearing inserts to ensure they are
not damaged. Fit of bearings should be determined
when engine is being assembled.
Assembly
There are two notches cast in the top of all piston
heads to facilitate proper installation. The pistons
should always be installed with the notches toward the
front of the engine (fig. 1B-31).
(1) Lubricate piston pin holes in piston and con
necting rod lightly with graphite lubricant.