Connecting Rod and Bearings

IMPORTANT:

The powdered metal connecting rod and cap are machined for proper clearances. The connecting rod and cap must be used as an assembly with no repair or modifications to either mating surface. Do not attempt to repair the rod or cap. If service is required, replace the connecting rod as an assembly.
Do not attempt to repair the bolt hole threads of the connecting rod.

Fig 1: Identifying Piston & Connecting Rod Components

Courtesy of GENERAL MOTORS CORP.

Clean the connecting rod (105) and cap (103) in solvent.

CAUTION: Refer to Safety Glasses Caution .

Dry the components with compressed air.
Inspect the connecting rod for the following conditions:

Fig 2: Identifying Connecting Rod Inspection Areas
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- Twisting (1)
- Proper fit of the connecting rod and cap mating surfaces (2)
- Nicks or gouges in the bearing bore (3)
- Damage to the bearing locating slots (4)
Measure the connecting rod bearing bore (1) for an out-of-round condition. Refer to Engine Mechanical Specifications (LR4 VIN V) or Engine Mechanical Specifications (LM7 VIN T) or Engine Mechanical Specifications (L33 VIN B) or Engine Mechanical Specifications (L59 VIN Z) or Engine Mechanical Specifications (LQ4 VIN U) or Engine Mechanical Specifications (LQ9 VIN N) .

Fig 3: Inspecting Connecting Rod Bearing Bore
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To determine full-floating piston pin-to-connecting rod bore clearance, use a micrometer and measure the piston pin outside diameter (OD).

Fig 4: Measuring Piston Pin Diameter
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To determine the full-floating piston pin-to-connecting rod bore clearance, use a micrometer and measure the connecting rod pin bore (1) inside diameter (ID).

Fig 5: Measuring Connecting Rod Pin Bore Inside Diameter
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Subtract the piston pin OD measurement from the connecting rod pin bore ID measurement to determine pin-to-bore clearance. Refer to Engine Mechanical Specifications (LR4 VIN V) or Engine Mechanical Specifications (LM7 VIN T) or Engine Mechanical Specifications (L33 VIN B) or Engine Mechanical Specifications (L59 VIN Z) or Engine Mechanical Specifications (LQ4 VIN U) or Engine Mechanical Specifications (LQ9 VIN N) .
Inspect the connecting rod bearings for craters or pockets. Flattened sections on the bearing halves indicate fatigue.

Fig 6: Identifying Crankshaft Bearing Craters Or Pockets
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Inspect the connecting rod bearings for excessive scoring or discoloration.

Fig 7: Identifying Connecting Rod Bearing Scoring Or Discoloration
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Inspect the connecting rod bearings for dirt or debris imbedded into the bearing material.
Inspect the connecting rod bearings for improper seating indicated by bright, polished sections of the bearing surface.

Fig 8: Crankshaft Bearing Polished Sections (Improper Seating)
Courtesy of GENERAL MOTORS CORP.