(12) Remove minor nicks and burrs from
piston by polishing with crocus cloth. Clean to re-
move abrasive residue.
Prior to. installation of piston assemblies
(13) If necessary, replace both piston pin and
of the piston, connecting rods and crank-
If new piston pin and bushing are used,
check connecting rod alignment on a
(1) Install upper half of main bearings (7 and
standard aligning fixture.
(14) Inspect piston for deep scores and
scratches and other damage.
Some of the bearings partially cover oil
(15) Insert each piston into its cylinder bore
with a piece of 1/2 x 0.0050 feeler ribbon. A force
of 5 to 8 pads should be required to remove each
(2) Carefully place crankshaft (12) into posi-
ribbon Replace all piston if any are not within the
(3) Place a short strip of plastic gauge on
each main bearing journal.
Cylinder bores may be rebored to accept
(4) Install lower half of main bearings, main
oversized pistons (paragraph 3-56).
screws (4 and 8).
(16) Fit each piston ring into place into its
cylinder bore and using a feeler gauge, measure
(5) Tighten screws (4) to 100 ft-lbs torque.
gap dimension Gap shall be 0.0100 to 0.0200 inch.
Tighten screws (8) to 130 ft-lbs torque.
If gap is under 0.0100 inch, file as follows:
(6) Remove main bearing caps and lower half
(a) Hold a file in a vise.
of main bearings. Check plastic gauge against stand-
(b) Grasp piston ring in both hands.
ard to determine main bearing clearance. Clearance
shall be 0.0009 to 0.0034 inch.
(c) Insert fi1e into ring gap and move
(7) If clearance is not within specified limits,
ring down the entire length of the file. Be sure to
apply equal pressure on the ring.
grind crankshaft and install with undersized bearings
(paragraph c(7) above).
(17) Roll each ring all the way around its
(8) When bearing clearances have been estab-
piston groove to check clearance. If clearance is in-
sufficient, lap the sides of the ring on a piece of
lished, install lower half of main bearings and main
No. 000 grit emery cloth laid on a flat surface.
bearing caps (step (5) above).
(1) Using a piston ring expander install oil
Apply a liberal coating of engine lubricating
control ring (23, figure 9-50), scraper ring (22) and
oil to inner surface of main bearings prior
compression rings (21) onto pistons (24).
(9) Use a feeler gauge to check crankshaft
end thrust clearance on center main bearing. End
If replacement piston rings have dots on
thrust clearance shall be 0.0050 to 0.0100 inch.
the rim, the rings should be installed
with the dots toward the piston head.
(10) If end thrust clearance is not as specified,
remove center main Bearing end polish sides on a
(2) Apply a light coat of engine oil to the
piece of crocus cloth. Clean to remove abrasive
bushing (19) and connecting rod (18) and press the
residue and apply a liberal coating of engine lubricat-
bushing into the connecting rod.
ing oil before installation.
(3) Fit piston assemblies (17) onto connecting
(11) Apply a liberal coating of engine Lubricat-
rods (18) and insert piston pins (16). Install retaining
ing oil to cylinder bores, pistons, piston rings and