GM Service Manual Online
For 1990-2009 cars only

Special Tools

    •  J-8037 Universal Piston Ring Compressor
    •  J-8087 Cylinder Bore Check Gauge
    •  J-24086-B Piston Pin Service Set
    •  KM-470-B Angular Torque Gauge

Removal Procedure


    Object Number: 1758698  Size: SH
  1. Remove the cylinder head with the intake manifold and exhaust manifold attached. Refer to Cylinder Head Replacement.
  2. Remove the oil pan. Refer to Oil Pan Replacement.
  3. Remove the oil suction pipe and the O-ring.

  4. Object Number: 1765847  Size: SH
  5. Remove the oil pan scraper.

  6. Object Number: 1765846  Size: SH
  7. Remove the crankshaft balancer unit assembly. Refer to Crankshaft Balancer Replacement.

  8. Object Number: 1765848  Size: SH
  9. Position the piston to the bottom of the piston stroke.
  10. Mark the connecting rod cap for position.
  11. Remove the connecting rod cap bolts.
  12. Remove the connecting rod cap and the lower connecting rod bearing.
  13. Remove the upper connecting rod bearing.

  14. Object Number: 1758700  Size: SH

    Note: Use care when handling the piston. Worn piston rings are sharp.

  15. Remove the piston.
  16. Expand the piston rings by using J-8037 universal piston ring compressor .
  17. Remove the piston rings.

  18. Object Number: 1758701  Size: SH
  19. Remove the piston pin from the piston and connecting rod assembly using the J-24086-B piston pin service set  (1).
  20. Separate the piston from the connecting rod.

Inspection Procedure


    Object Number: 1758705  Size: SH
  1. Inspect the pistons for the following conditions:
  2. • Eroded areas at the top of the piston
    • Worn piston pin bores or worn piston pins
    • Scuffed or damaged skirt coating
    • Ring grooves for cracks, nicks or burrs that may cause binding
    • Warped or worn ring lands
  3. Replace pistons that show any signs of damage or excessive wear.

  4. Object Number: 1758709  Size: SH
  5. Measure the piston width using the following procedure:
  6. • Using an outside micrometer, measure the width of the piston at the thrust surfaces of the piston, perpendicular to the piston pin centerline.
    • Compare the measurement of the piston to its original cylinder by subtracting the piston width from the cylinder diameter.
    • If the clearance obtained through measurement is greater than the provided specifications and the cylinder bores are within specification, replace the piston.

    Object Number: 1758710  Size: SH
  7. Measure the piston pin bore to piston pin (2) clearances using the following procedure:
  8. • Piston pin bores and pins must be free of varnish or scuffing.
    • Use an outside micrometer (1) to measure the piston pin in the piston contact areas.

    Object Number: 1758711  Size: SH
  9. Using an inside micrometer, measure the piston pin bore. Compare the result with the piston pin diameter and piston pin to piston pin bore clearance. Refer to Engine Mechanical Specifications.
  10. • If the clearance is excessive, determine which piece is out of specification and replace as required.
    • Replace the piston if any of its dimensions are out of specification.
    • If the new piston does not meet clearance specifications, the cylinder block may need to be oversized to 0.25. There is only one size of oversized pistons and rings available for service.

    Object Number: 1758715  Size: SH
  11. Measure the piston ring end gap using the following procedure.
  12. • Piston pin bores and pins must be free of varnish or scuffing.
    • Place the piston ring (1) in the area of the bore where the piston ring will travel, approximately 25 mm below the deck surface. Ensure the ring is square with the cylinder bore by positioning the ring with the piston head.
    • Measure the end gap of the piston ring with feeler gauges (2).
    • If the clearance exceeds the provided specifications, the piston rings must be replaced.
    • Repeat the procedure for all piston rings.

    Object Number: 1758720  Size: SH
  13. Measure the piston ring side clearance using the following procedure.
  14. • Roll the piston ring (1) entirely around the piston ring groove. If any binding is caused by the ring groove, dress the groove with a fine file. If any binding is caused by a distorted piston ring, replace the ring.
    • With the piston ring on the piston, use feeler gauges (2) to check clearance at multiple locations.
    • Compare the measurements with piston ring side clearance. Refer to Engine Mechanical Specifications.
    • If the clearance is greater than specifications, replace the piston rings.
    • If the new ring does not reduce the clearance to the correct specification, install a new piston.
    • If the new piston does not meet clearance specifications, the cylinder block may need to be oversized to 0.25 mm. There is only one size of oversized pistons and rings available for service.

    Object Number: 1758721  Size: SH
  15. Inspect the connecting rods for the following conditions.
  16. • Inspect the connecting rod beam for twisting or bending.
    • Inspect the rod cap for any nicks or damage caused by possible interference.
    • Inspect for scratches or abrasion on the rod bearing seating surface.
    • If the connecting rod bores contain minor scratches or abrasions, clean the bores in a circular direction with a light emery paper.
    • Retain the original bolts for preliminary assembly. They must be replaced for final assembly.

    Object Number: 1758710  Size: SH
  17. Measure the connecting rod piston pin bore to piston pin clearance using the following procedures.
  18. Using an outside micrometer (1), take two measurements of the piston pin (2) in the area of the connecting rod contact.


    Object Number: 1758723  Size: SH
  19. Using an inside micrometer, measure the connecting rod piston pin bore (1).
  20. • Subtract the piston pin diameter from the piston pin bore.
    • Compare the clearance measurements. Refer to Engine Mechanical Specifications.
    • If the clearance is excessive, replace the piston pin. If a new pin does not resolve the clearance problem, replace the connecting rod.

    Object Number: 1758725  Size: SH
  21. Measure the connecting rod crankshaft bearing bore (1) using the following procedures.
  22. • Using an inside micrometer, measure the connecting rod crankshaft bearing bore.
    • Compare the bore measurements. Refer to Engine Mechanical Specifications.
    • Replace the connecting rod if the bore is out of specification. Do not recondition the connecting rod.

    Object Number: 1758726  Size: SH
  23. Inspect the engine block deck surface for flatness using a straight edge and a feeler gage. Refer to Engine Mechanical Specifications.
  24. Inspect the bearing bore for concentricity and alignment using J-8087 cylinder bore check gauge . Refer to Engine Mechanical Specifications. If the bearing bore is beyond the specifications, replace the engine block.
  25. Inspect the engine block cylinder bore for wear, runout, ridging and taper using a bore gage. Refer to Engine Mechanical Specifications.
  26. Inspect the engine block cylinder bore for glazing. Lightly hone the cylinder bore as necessary.

Installation Procedure


    Object Number: 1758701  Size: SH

    Note: For ease of installation of the piston pin, the connecting rod should be heated to 280°C (536°F). Heat the upper connecting rod only. Use commercial thermo color material to determine the correct temperature. When the thermo color material changes from black to green, the temperature is correct for installation.

  1. Align the notch on the piston and connecting rod so that the proper sides will be facing the front of the engine.
  2. Install the piston pin guide through the piston and the connecting rod.
  3. Coat the piston pin with clean oil.
  4. Install the piston pin into the opposite side of the piston.
  5. Install the piston pin into the piston and connecting rod assembly using the J-24086-B set .

  6. Object Number: 1758729  Size: SH
  7. Select a set of new piston rings.
  8. Install the piston oil ring, the expander, then the second piston oil ring to the bottom ring groove of the piston.
  9. Install the second compression ring to the middle ring groove of the piston.
  10. Install the top compression ring to the top ring groove of the piston.

  11. Object Number: 1758730  Size: SH
  12. Use the piston ring expander to install the piston rings. Do not expand the piston rings beyond the expansion necessary for installation.
  13. Stagger the piston oil rings, the oil ring rail gaps, the second compression ring and the top compression ring in relation to the notch on the top of the piston.

  14. Object Number: 1758733  Size: SH
  15. Lubricate the cylinder wall and the piston rings with clean engine oil.
  16. Install the piston using J-8037 compressor and a wooden handle. Guide the lower connecting rod end to prevent damaging the crankshaft journal.
  17. Install the connecting rod cap and bearings. Refer to Crankshaft and Bearing Cleaning and Inspection.
  18. Caution: Refer to Fastener Caution in the Preface section.


    Object Number: 1765848  Size: SH
  19. Install the connecting rod cap bolts and tighten to 35 N·m (26 lb ft).
  20. Using KM-470-B angular torque gauge , tighten the bolts one turn of 45 degrees plus one turn of 15 degrees.


    Object Number: 1765846  Size: SH
  21. Install the KM-470-B gauge and tighten the crankshaft balancer unit assembly bolts to 20 N·m (15 lb ft)and turn the bolts another 45 degrees using KM-470-B gauge .

  22. Object Number: 1765847  Size: SH
  23. Install the oil pan scraper bolts and tighten to 8 N·m (7 lb in).

  24. Object Number: 1758698  Size: SH
  25. Install the oil suction pipe with the new O-ring and tighten the bolts to 8 N·m (7 lb in).

  26. Object Number: 1758625  Size: SH
  27. Install the oil pan. Refer to Oil Pan Replacement.
  28. Install the cylinder head with the intake manifold and exhaust manifold attached. Refer to Cylinder Head Replacement.