TM 5-3810-294-34
mandril. Lay the rods flat in the mandril and check for
from one gap to another.
twisting malformation by inserting feeder gages between
d. Coat piston, piston ring compressor and sleeve
the rod and mandril. Malformation of 0.004 inch or
with oil. Install piston and rod assembly through top of
greater is cause for rejecting the rod.
crankcase.
i. Inspect the pistons for cracks, breaks, or scores.
e. Replace bearing shell halves (11, 12, and 13), and
Check piston ring grooves and piston ring lands-for wear
thrust washer (11), in the bore of the crankcase and
using a new piston ring and feeler gage.
bearing caps. Be sure the shells are fully seated, oil
j. Inspect piston pin for wear and sign of etching.
holes are alined, and the locking tangs on the bearings fit
k. Inspect all bushings for burrs and mars, dress off
into the recesses. Apply a film of engine oil on the
any such unevenness.
bearing shells and place the crankshaft into position,
l. Measure the piston skirt at right angles to the pin
Note. Index the timing marks on the crankshaft
holes to determine if it is worn.
m.
Check cylinder bore with inside-reading
gear and camshaft gear.
micrometer to determine taper, out of round, or worn
condition.
f. Install bearing caps (3, 4, and 5) over the crankshaft
n. Inspect piston rings for damage.
journals being sure that the caps are in their correct
positions with the number side of the caps to the
4-37. Repair and Replacement
camshaft side of the engine. Secure lightly with washers
a. Refer to TM 5-3810-294-34P for repair parts.
(2) and bolts (1).
b. Replace camshaft if bearings are worn, lobes are
g. Install rod bearings (9), caps (8), and rod cap bolt
worn or cracked, or gear teeth are cracked,
(7).
broken, or worn. Replace comshaft gear if teeth are
cracked, broken, or worn.
Note. Be sure rod cap bolt threads are in good
c. Remove nicks and marks from bearings and
condition. Be sure blind holes in rod (36) are clean of
bearing surfaces. Replace worn or defective bearings.
chips and dirt. Refer to table 1-4 for rod side clearance.
d. Replace twisted or distorted rods.
Torque bolts to 80 foot-pounds.
e. Replace pistons if cracked, or if ring grooves are
damaged. Replace piston pins if mutilated or worn.
h. Place camshaft plate (18) on camshaft and install
Replace cracked or damaged piston rings.
camshaft gear key (20). Heat the camshaft gear in
f. Replace all capscrews that have been damaged or
boiling water and install the gear (17) (with the timing
show evidence of mutilated threads or distortion.
mark facing away from the shaft) on the camshaft.
4-38. Reassembly and Installation
i. Install camshaft bearings (22, 23, 24, and 25) using
Refer to figure 4-6 and reassemble and install as follows.
camshaft bushing tool.
a. Install sleeves (36).
j. Coat the camshaft and lobes with heavy duty axle
b. Install piston pin bushing (34) in rod (35). Heat
lubricant. Install the camshaft into the crankcase being
piston in hot water to approximately 150 degrees F, and
sure that the timing mark on the camshaft gear is
push piston pin through piston and rod bushing, alining
correctly indexed with the timing mark on the crankshaft
the bushing and rod bore with piston pin holes in the
gear. Secure thrust plate to crankcase with capscrews
piston, and push the piston pin (32) completely into
(19). Check camshaft and play and gear backlash
position through rod (35). Install retainer (28).
against values given in table 1-4.
c. Install rings (31, 30 and 29) into piston grooves
k. Install retainer (16) and secure with nut (15).
using a piston ring expander. Position the rings so that
the gaps are 90 degrees from the thrust side of the
piston (in line with the piston pin bore) and 180 degrees
Section VII. REPAIR OF ENGINE CRANKCASE
4-39. Description
4-40. Disassembly
The crankcase supports the crankshaft in true alignment,
Refer to figure 4-7 and disassemble crankcase as
and provides the housing for the pistons and driving
follows.
components.
4-12
