TM 9-2320-272-24-4
5-26. PISTON AND CONNECTING ROD MAINTENANCE (Contd)
c. Cleaning and Inspection
For general cleaning instructions, refer to para. 2-14.
1.
2.
For general inspection instructions, refer to para. 2-15.
3.
Replace all parts failing inspection.
NOTE
Measurements to check piston skirt outside diameters are taken
at right angle to piston pin bore.
4.
Measure outside diameter of piston skirt (3) at several places. If diameter is less than 4.479 in.
(113.8 mm), replace piston (4).
5.
Check piston ring groove (5) for wear.
a. Insert keystone gauge into ring groove (5).
b. If shoulders of keystone gauge touch either end of ring groove (5), replace piston (4).
6.
Check compression ring (6) and oil ring (7) grooves for wear.
a. Insert new compression ring (1) into compression ring groove (6).
b. Try to insert 0.006 in. (0.152 mm) feeler gauge between compression ring (1) and compression
ring groove (6).
c. If feeler gauge enters compression ring groove (6) without force, replace piston (4).
d. Repeat steps a through c using new oil ring (2) and 0.005 in. (0.127 mm) feeler gauge to check oil
ring groove (7) for wear.
Measure inside diameter of piston pin bore (9). If inside diameter exceeds 1.773 in. (45.03 mm),
7.
replace piston (4).
Measure outside diameter of piston pin (8). If outside diameter exceeds 1.771 in. (44.98 mm),
8.
replace piston pin (8).
Inspect I-beam section (15) of connecting rod (11) for nicks, dents, and gouges. If nicked, dented, or
9.
gouged, replace connecting rod (11).
Install two connecting rod screws (12) in connecting rod (11).
10.
Install connecting rod cap (14) on connecting rod (11) with two nuts (13). Tighten nuts (13) to
11.
73 lb-ft (99 Nm).
Check crankshaft journal bore (10) of connecting rod (11) for wear:
12.
a. Measure inside diameter of crankshaft journal bore (10) at several points 30 from each other.
b. If inside diameter measurement exceeds 2.9926 in. (76.012 mm), replace connecting rod (11).
Measure inside diameter of piston pin bore (16). If inside diameter exceeds 1.773 in. (45.03 mm),
13.
replace connecting rod (11).
Remove two nuts (13) and connecting rod cap (14) from connecting rod (11).
14.
Check connecting rod journals (18) on crankshaft (17) for wear.
15.
a. Measure outside diameter of six connecting rod journals (18) at A-A and B-B. If difference
exceeds 0.0005 in. (0.013), replace crankshaft (17) (para. 5-29).
b. Measure outside diameter of six connecting rod journals (18) at C-C and D-D. If difference
exceeds 0.002 in. (0.05 mm), replace crankshaft (17) (para. 5-29).
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