ARMY TM 9-2815-253-24
AIR FORCE TO 38G1-93-2
MARINE CORPS TM 2815-24/3
Remove two capscrews (1), connecting rod (3), and bearing cap (2).
If damaged or worn, remove bearing halves (4).
Carefully scrape any build up of carbon from top of cylinder bore.
Rotate crankshaft until piston is at TDC.
Install (hand-tighten) a capscrew (1) into nearest connecting rod bearing cap bolt hole.
Using a suitable lever against crankcase and end of capscrew, press down on end of lever until piston rings are
clear of cylinder bore.
Lift out piston (5) and connecting rod (3) and tag with corresponding cylinder number.
Install bearing cap (2) onto connecting rod (3).
3-30.2. Inspect and Measure.
Thoroughly clean cylinder barrel. Check for scoring and wear.
Clean piston (5, FIGURE 3-36) by removing all traces of carbon from both upper and underside of crown and ring
Check for correct gap clearance. Refer to TABLE 3-6, with piston rings (6) in an unworn section of cylinder
Clean connecting rod (3).
Check bushing (9) for wear. Replace if worn.
If big end has been disassembled because of metal failure, oil passages in crankshaft must also be examined for
obstruction and fragments of metal.
The maximum advisable piston to cylinder clearance given is the clearance between the bottom of
the piston skirt, across the faces, and the cylinder bore measured in the region of travel of the
piston skirt. The clearance is not to be measured at the top of the bore. When cylinders are
rebored, the lower skirt should be etched or painted with the amount of the oversize.
The ring gaps given in TABLE 3-6 are those to be anticipated when checking rings in an unworn
part of the bore. For every 0.01 mm (0.0004 in.) by which the actual bore size exceeds the initial
dimension, the ring gap will increase by approximately 0.03 mm (0.0012 in.) The firing ring side
clearance is measured with a new ring flush with the top piston land.
Oversize pistons and piston rings, and undersize big end and main bearing shells are available.
Nonstandard sizes are marked, by the amount they are under or oversize, as a suffix to the part
numbers which can be found in the following locations:
Piston Rings - stamped on the face of the ring.
Pistons stamped on the top surface.
Bearings stamped on the steel outside surface of the bearing.
Using appropriate measuring devices, check components listed in TABLE 3-6 for wear. Replace components
that exceed maximum clearance.