Connecting Rod Inspection.

between aligner face and skirt of piston. If this space is

NOTE

not equal distance, rod is twisted out of line.

When measuring clearance between

NOTE

a piston and a used sleeve. make

Ring lands at top of piston are

certain that piston is inserted into the

smaller than skirt: therefore, check

sleeve far enough so measurement is

alignment of rod along full length of

taken in area of piston ring travel

skirt only.

within sleeve.

(3) Twist rod with bending bar until space

(5) Piston skirt diameter of a new piston is

between aligner face and piston skirt is even.

3.4365 inches to 3.4385 inches, measured at right

(4) Check for twist in the opposite diagonal

angles to the piston pin; inside diameter of a new

line to piston rod (piston head pointing up). Observe

cylinder sleeve is 3.4379 inches to 3.4385 inches.

space between aligner face and piston skirt. If space is

Deviation from these measurements will indicate amount

uneven, twist rod with bending bar until true alignment is

of wear on piston or cylinder sleeve. The piston or

obtained.

cylinder sleeve, or both, must be replaced if the

(5) Check for bent rod by moving piston into

clearance exceeds 0.008 inch.

parallel position with connecting rod and observe space

(6) New piston rings must always be used

between aligner face and piston skirt. If space is not

with new pistons. If engine has been in service for some

even, straighten rod carefully with bending bar.

time, even though the same pistons are used again, it is

g. Fitting Pistons to Cylinder Sleeves.

advisable to use new rings when the engine is

CAUTION

reassembled.

Measurement of pistons and cylinder

e. Connecting Rod Inspection.

(1) Wash connecting rod assembly with SD.

sleeves (2, fig. 3-32), and running

(2) Measure outside diameter (OD) of piston

clearances between them should be

pin to determine wear. Specified diameter of a new

taken at room temperatures. Pistons

piston pin is 0.8591 inch to 0.8591 inch.

are cam ground and can be from

(3) Specified inside diameter of connecting

0.0006 inch tight to 0.002 inch loose

rod bushing is 0.8593 inch to 0.8596 inch. These pin

when fitted to their respective

and bushing dimensions provide a clearance of 0.0001

cylinder sleeves before piston rings

inch to 0.0005 inch; clearances of up to 0.002 inch are

are installed. Insufficient clearance

permissible. If clearance is close to or beyond this limit,

will result in premature failure of

replace connecting rod bushing.

these parts.

(4) Inspect connecting rod bearings (10, fig.

(1) Measure cylinder sleeves (para 3-20).

3-35) for scoring, chipping, corrosion, cracking, or signs

(2) Measure pistons (para d above).

of overheating; discard bearing shells if any of these

NOTE

conditions are apparent.

Pistons and cylinder sleeves are

(5) Back of rod bearings should be inspected

available in standard size. 0.020 inch,

for bright spots and discarded if any are found, as this

and 0.040 inch oversize.

condition indicates they have been moving in their

h. Fitting Piston Rings.

supports. Inspect rod bearings for wear. Specified

(1) Gap between ends of piston rings should

inside diameter of rod bearings when installed with

be measured before rings are installed on piston. Select

bearing cap retaining bolts tightened to specified torque

rings to be installed on each piston, oil and insert them

is 2.1239 inches to 2.1254 inches. This provides a

one at a time into cylinder sleeve in which they are to

running clearance of 0.0015 inch to 0.0030 inch; new

operate. Use a piston to push ring squarely into cylinder

bearings must be installed when this clearance exceeds

sleeve so that it is parallel with top of cylinder block.

0. 006 inch. Refer to paragraph 3-21 and measure the

(2) Push ring far enough down in bore of

connecting rod bearings for wear and clearance with the

cylinder sleeve to be on ring travel area. Measure ring

crankshaft in a similar manner. If crankshaft is worn or

gap with a feeler gauge.

damaged it must be replaced.

(3) Minimum ring gap on all rings is 0.011

f. Piston Rod Alignment Inspection.

inch. If necessary, file ring ends with a fine cut file to

(1) If wear on rod bushings or bearings

obtain correct clearance.

indicates rod may be out of alignment, place rod and

(4) Measure ring-to-groove clearance (top of

piston on aligning fixture for checking.

ring to top of groove in piston ). Specified clearances are

(2) With piston and connecting rod assembly

as follows: top compression ring, 0.002 inch to 0.004

clamped onto aligning fixture, swing rod into a horizontal

inch; second compression ring, 0.0015 inch to 0.0035

position parallel to floor. With piston held diagonally to

inch; and oil control rings, 0.001 inch to 0.003 inch.

rod (piston head pointing to floor), observe space

(5) After rings have been properly fitted,

3-43