Dodge RAM TRUCK 1500 1995 Service Manual page 977

I - 138 8 J L ENGINE
BR
(2) Position the oil pump cover onto the timing
chain cover. Tighten cover bolts to 14 N°m (125 in,
lbs.) torque.
(8) Make sure that inner ring moves freely after
cover is installed.
(4) Install the timing chain cover.
(5) Squirt oil into relief valve hole until oil runs
out.
(6) Install the relief valve and spring.
(7) Using a new pressure relief valve gasket, in­
stall the relief valve plug. Tighten the plug to 20 N*m
(15 ft. lbs.) torque.
(8) Install oil filter that has been filled with oil.
PISTON AND CONNECTING ROD ASSEMBLY
The pistons are elliptically turned so that the di­
ameter at the pin boss is less than its diameter
across the thrust face. This allows for expansion un­
der normal operating conditions. Under operating
temperatures, expansion forces the pin bosses away
from each other, causing the piston to assume a more
nearly round shape.
All pistons are machined to the same weight, re­
gardless of size, to maintain piston balance.
The piston pin rotates in the piston only and is re­
tained by the press interference fit of the piston pin
in the connecting rod.
The pistons have a unique dry-film lubricant coat­
ing baked onto the skirts to reduce friction. The lu­
bricant is particularly effective during engine break-
in, but with time, the material becomes embedded
into cylinder bore walls and continues to reduce fric­
tion.
REMOVAL
" (1) Eemove the engine from the vehicle (refer to
Engine Eemoval of this manual).
(2) Remove the valve cover, rocker arms, push rods
and cylinder head. Mark parts as removed.
(3) Remove the oil pan and oil pump pick-up tube.
(4) Remove top ridge of cylinder bores with a reli­
able ridge reamer before removing pistons from cyl­
inder block. Be sure to keep tops of pistons covered
during this operation.
(5) Be sure the connecting rod and connecting rod
cap are identified with the cylinder number. Remove
connecting rod cap. Install connecting rod bolt guide
set on connecting rod bolts.
(6) Pistons and connecting rods must be removed
from top of cylinder block. When removing piston and
connecting rod assemblies, rotate crankshaft center
the connecting rod in the cylinder bore and at BDC.
Be careful not to nick crankshaft journals. DO
NOT try to remove Mack coating on skirt. This
is the dry film lubricant.
(7) After removal, install bearing cap on the mat­
ing rod.
INSPECTION
Check the crankshaft connecting rod journal for ex­
cessive wear, taper and scoring.
Check the cylinder block bore for out-of-round,
taper, scoring and scuffing.
FITTING PISTONS
Piston and cylinder wall must be clean and dry.
Specified clearance between the piston and the cylin­
der wall is 0.013-0.038 mm (0.0005-0.0015 inch).
Piston diameter should be measured at the top of
skirt, 90° to piston pin axis. Cylinder bores should be
measured halfway down the cylinder bore and trans­
verse to the engine crankshaft center line.
Pistons and cylinder bores should be measured at
normal room temperature, 2PC (70°F).
(1) To correctly select the proper size piston, a cyl­
inder bore gauge, Special Tool 6879 or equivalent, ca­
pable of reading in .0001" INCREMENTS is required.
If a bore gauge is not available, do not use an inside
micrometer.
The coating material is applied to the piston after
the final piston machining process. Measuring the
outside diameter of a coated piston will not provide
accurate results. Therefore measuring the inside di­
ameter of the cylinder bore with a dial Bore Gauge is
MANDATORY.. To correctly select the proper size
piston, a cylinder bore gauge capable of reading in
.0001" increments is required.
Piston installation into the cylinder bore require
slightly more pressure than that required for non-
coated pistons. The bonded coating on the piston will
give the appearance of a line-to-line fit with the cyl­
inder bore.
B
J9509-125
Fig. 14 Bore Gauge