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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 589 (Engine Mechanical - 2.2L) >> Removal And Installation >> Unit Repair Cleaning, Inspection, And Selection >> Piston, Connecting Rod And Bearings Clean And Inspect (Unit Repair) >> Piston Measurement

Piston Measurement

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Clean piston skirts and pins with a cleaning solvent. DO NOT wire brush any part of the piston.
  2. Clean piston ring grooves with a groove cleaner. Make sure oil ring holes and slots are clean.
  3. Inspect pistons for the following conditions:
    • Cracked ring lands, skirts, or pin bosses
    • Ring grooves for nicks, burrs that may cause binding
    • Warped or worn ring lands
    • Eroded areas at the top of the piston
    • Scuffed or damaged skirts
    • Worn piston pin bores
    Fig 1: Inspecting Piston
    G01039571Courtesy of GENERAL MOTORS CORP.
  4. Replace pistons that show any signs or damage or excessive wear.
  5. Measure piston pin bore to piston pin clearances using the following procedure:
    1. 5.1 Piston pin bores and pins must be free of varnish or scuffing.
    2. 5.2 Use an outside micrometer to measure the piston pin in the piston contact areas.
    3. 5.3 Using an inside micrometer, measure the piston pin bore.
    4. 5.4 Subtract the measurement of the piston pin bore from the piston pin. The clearance should be within 0.002-0.012 mm (0.00007-0.00047 in.).
    5. 5.5 If the clearance is excessive, determine which component is out of specification.
  6. Measure the piston ring end gap using the following procedure:
    1. 6.1 Place the piston ring in the area of the bore where the piston ring will travel (approximately 25 mm or 1 in. down from the deck surface). Be sure the ring is square with the cylinder bore by positioning the ring with the piston head.
    2. 6.2 Measure the end gap of the piston ring with feeler gages. Compare the measurements with those provided below:
    • The top compression ring end gap should be 0.20-0.40 mm (0.0060-0.015 in.).
    • The second compression ring end gap should be 0.35-0.55 mm (0.0137-0.0216 in.).
    • The oil ring end gap should be 0.25-0.76 mm (0.0098-0.029 in.).
    1. 6.3 If the clearance exceeds the provided specifications, the piston rings must be replaced.
    2. 6.4 Repeat the procedure for all the piston rings.
      Fig 2: Measuring The Piston Ring End Gap
      G01039572Courtesy of GENERAL MOTORS CORP.
  7. Measure the piston ring side clearance using the following procedure:
    1. 7.1 Roll the piston ring entirely around the piston ring groove. If any binding is caused by a distorted piston ring, replace the ring.
    2. 7.2 With the piston ring on the piston, use feeler gages to check clearance at multiple locations.
    3. 7.3 The clearance between the surface of the top piston ring and the ring land should be no greater than 0.075 mm (0.0030 in.).
    4. 7.4 If the clearance is greater than specifications, replace the piston ring.
    5. 7.5 If the new ring does not reduce the top ring side clearance to 0.075 mm (0.0030 in.) or less, install a new piston.
  8. The top compression ring may be installed with either side up. There is a locating dimple on the 2nd compression ring near the end for identification of the top side. Install the 2nd compression ring with the dimple facing up.
  9. The clearance between the surface of the second piston ring and the ring land should be no greater than 0.069 mm (0.0026 in.).
  10. If the new ring does not reduce the clearance to 0.069 mm (0.0026 in.) or less, install a new piston.
    Fig 3: Measuring The Piston Ring Side Clearance
    G01039573Courtesy of GENERAL MOTORS CORP.
  11. Measure piston width using the following procedure:
    1. 11.1 Using an outside micrometer, measure the width of the piston 14.5 mm (0.570 in.) above the bottom of the piston skirt at the thrust surface perpendicular to the centerline of the piston pin.
    2. 11.2 Compare the measurement of the piston to its original cylinder by subtracting the piston width from the cylinder diameter.
    3. 11.3 The proper width specification for the piston is 85.967-85.982 mm (3.3845-3.3851 in.).
  12. If the clearance obtained through measurement is greater than these specifications and the cylinder bores are within specification, replace the piston.
    Fig 4: Measuring Piston Width
    G01039574Courtesy of GENERAL MOTORS CORP.
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