Figure 3-11. Ring groove wear check.

*TM 9-2815-213-34

(5) Check bolt pad corner radius (0.25 0.2700

inch). If radius does not check to tolerance, machine to

proper dimensions.

k. Inspect connecting rod bearing caps using ball

point micrometer, dial indicator thickness gage, or

Comparator. Refer to paragraph 3-177, for shell

thickness and allowable wear.

l. Inspect pistons for scoring,

burning,

damaged ring grooves and cracks inside piston struts. A

badly scored piston must be replaced; a slightly scored

piston may be cleaned and reused.

m. Inspect top of piston for burned spots indications

of over-heating such as carbon formation on underside

of the piston. Replace burned pistons.

n. Using ring groove wear gage (52, fig. 28) check

groove wear as follows: (fig. 3-11)

(1) Insert ring groove wear gage (52, fig. B-

28) into each of the top and second ring grooves.

Figure 3-12. Piston ring gap check.

(2) If shoulders of gage touch ring grooves

lands, piston must be discarded.

NOTE

Measurement should be

taken at

ambient air temperature

of 70/90

degrees Fahrenheit.

q. Using inside micrometer, measure piston pin

bore; discard piston if bore exceeds 2.005-inch.

3-16. Repair

Repair of the connecting rod and piston assembly is

limited to general procedures as outlined in paragraph 2-

7. Any defect, or measurement outside the tolerances

listed in repair and rebuild standards (paras. 3-177, and

3-178) is cause for replacement. If piston pin bushings

must be replaced use bushing driver (46, fig. B-28) for

bushing removal and replacement. Check with plug

gage (50, fig. B-28).

3-17. Assembly

Figure 3-11. Ring groove wear check.

Assemble rod to piston in reverse order of paragraph 3-

13.

o. Check ring gap as follows:

NOTE

(1) Insert each compression ring into worn

portion of cylinder liner, seating it squarely using a piston

When installing rings insure the word

head (fig. 3-12).

"Top" inscribed on the ring, is to the top

(2) Measure ring gap with feeler gage. The

of the piston.

allowable ring gap is 0.013/0.0230: Rings exceeding this

limit should be discarded.

3-18. Installation

(3) If necessary, file ring ends to obtain gap of

a. Lubricate rod and piston assembly with OE- 10

0.0130/0.0230 inch.

lubricant.

p. Measure piston skirt diameter with micrometer at

b. Compress piston rings with suitable cylindrical

right angle to piston pin bore. Refer to paragraph 3-178,

ring compressor.

for wear limits. If piston wear exceeds 0.004-inch

c. Remove connecting rod cap from bolts and

discard piston.

make certain bolt heads are seated squarely on rod

shoulder. These parts are not interchangeable (fig. 3-

26).

3-7