GM Service Manual Online
For 1990-2009 cars only

Tools Required

    • J 8037 Piston Ring Compressor
    • J 8087 Cylinder Bore Gauge

Piston Selection


    Object Number: 4972  Size: SH

    Important: Measurements of all components should be taken with the components at normal room temperature.

    For proper piston fit, the engine block cylinder bores must not have excessive wear or taper.

    A used piston and pin set may be reinstalled if, after cleaning and inspection, they are within specifications.

  1. Inspect the engine block cylinder bore. Refer to Engine Block Cleaning and Inspection .
  2. Inspect the piston and the piston pin. Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection .
  3. Using the J 8087 measure the cylinder bore diameter. Measure at a point 64 mm (2.5 in) from the top of the cylinder bore.

  4. Object Number: 4974  Size: SH
  5. Measure the J 8087 with a micrometer and record the reading.

  6. Object Number: 4988  Size: SH
  7. With a micrometer or caliper at a right angle to the piston, measure the piston 42 mm (1.68 in) from the top of the piston.
  8. Subtract the piston diameter from the cylinder bore diameter in order to determine piston-to-bore clearance.
  9. For proper piston-to-bore clearance refer to Engine Mechanical Specifications .
  10. If the proper clearance cannot be obtained, select another piston and measure for the clearances.
  11. If the proper fit cannot be obtained, hone the cylinder bore or replace the cylinder block.
  12. When the piston-to-cylinder bore clearance is within specifications, mark the top of the piston using a permanent marker for installation to the proper cylinder.
  13. Refer to Separating Parts.

Installation Procedure


    Object Number: 4327  Size: SH
  1. Install the connecting rod bearings. Use the proper size bearings.
  2. 1.1. Install the bearing inserts into the connecting rod and the connecting rod cap.
    1.2. Lubricate the connecting rod bearings with engine oil.

    Object Number: 4326  Size: SH
  3. Install the piston and the connecting rod to the correct bore.
  4. 2.1. Slide a piece of 9.5 mm (0.375 in) fuel or vacuum hose over the connecting rod bolts. This protects the crankshaft journal during piston and connecting rod installation.
    2.2. Stagger each piston ring end gap equally around the piston.
    2.3. Lubricate the piston and the piston rings with engine oil.
    2.4. Install J 8037 over the piston. Do not disturb the piston ring end gap location.
    2.5. The piston must be installed so that the mark on the top of the piston faces the front of the engine.
    2.6. Place the piston in its matching bore.
    2.7. Tap the piston into its bore with a hammer handle. Guide the connecting rod to the connecting rod journal while tapping the piston into place.
    2.8. Hold the J 8037 against the engine block until all the rings have entered the cylinder bore.
    2.9. Remove the vacuum hose from the connecting rod bolts.

    Object Number: 182742  Size: SH

    Important: Ensure that the connecting rod cap is properly oriented on the connecting rod. The tab on the connecting rod should be oriented toward the left (exhaust manifold) side of the engine.

  5. Install the connecting rod cap.
  6. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  7. Install the connecting rod bolt nuts.
  8. Tighten

    1. Tighten the connecting rod bolt nuts to 52 N·m (38 lb ft).
    2. Loosen the connecting rod bolt nuts 1 full turn.
    3. Tighten the connecting rod bolt nuts to 52 N·m (38 lb ft).

    Object Number: 4328  Size: SH
  9. Measure the connecting rod side clearance with a feeler gauge.
  10. The correct clearance is 0.10-0.38 mm (0.0039-0.0149 in).