Piston, Pin, and Piston Rings

IMPORTANT:

Replace pistons, pins, and connecting rods that are damaged or show signs of excessive wear.
Do not wire brush any part of the piston.
Measurement of the components should be taken with the components at normal room temperature.

Fig 1: Identifying Piston & Connecting Rod Components

Courtesy of GENERAL MOTORS CORP.

Clean the varnish and carbon from the piston (107) using cleaning solvent.

CAUTION: Refer to Safety Glasses Caution .

Dry the components with compressed air.
Clean the piston ring grooves with a suitable ring groove cleaning tool.

Fig 2: Cleaning The Piston Ring Grooves With Suitable Ring Groove Cleaning Tool
Courtesy of GENERAL MOTORS CORP.
Clean the oil lubrication holes and slots.
Inspect the piston for the following conditions:

Fig 3: Identifying Piston Damage Inspection Areas
Courtesy of GENERAL MOTORS CORP.
- Cracks in the piston ring lands, the piston skirt, or pin bosses
- Piston ring grooves for nicks, burrs, or warpage which may cause the piston ring to bind-MINOR imperfections may be removed from the piston with a fine file.
- Scuffed or damaged skirts (2)
- Eroded areas at the top of the piston (1)
- Scoring to the full-floating design piston pin bore (3) or piston pin
Insert the edge of the piston ring into the piston ring groove.

Fig 4: Inserting Piston Ring Into Ring Groove
Courtesy of GENERAL MOTORS CORP.

Roll the piston ring completely around the piston. If binding is caused by distorted ring groove, MINOR imperfections may be removed with a fine file. If binding is caused by a distorted piston ring, replace the rings, as required.
Measure the piston ring side clearance with a feeler gage. If side clearance is not within specifications, try another piston ring. If the proper ring-to-groove clearance cannot be obtained, replace the piston, pin, and connecting rod assembly. 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 5: Measuring Piston Ring Side Clearance
Courtesy of GENERAL MOTORS CORP.
To determine piston pin-to-bore clearance, use a micrometer and measure the piston pin outside diameter (OD).

Fig 6: Measuring Piston Pin Diameter
Courtesy of GENERAL MOTORS CORP.
To determine the piston pin-to-bore clearance, use an inside micrometer and measure the piston pin bore inside diameter (ID).

Fig 7: Measuring The Piston Pin Bore
Courtesy of GENERAL MOTORS CORP.
Subtract the piston pin OD measurement from the piston 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) .