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Piston Measurement

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora and 2001 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. Measure piston width using the following procedure:
    1. 1.1. Using an outside micrometer, measure the width of the piston at 38 mm (1) (1.5 in) below the crown, top, at the thrust surfaces of the piston, perpendicular to the piston pin centerline.
    2. 1.2. Compare the measurement of the piston to its original cylinder by subtracting the piston width from the cylinder diameter.
    3. 1.3. Check your measurements with the Engine Mechanical Specifications .
    4. 1.4. If the clearance obtained through measurement is greater than the provided specifications and the cylinder bores are within specification, replace the piston.
    Fig 1: Measuring Piston Width
    G01815183Courtesy of GENERAL MOTORS CORP.
  2. Measure the piston pin bore to piston pin clearances using the following procedure:
    1. 2.1. Piston pin bores and pins must be free of varnish or scuffing.
    2. 2.2. Use an outside micrometer to measure the piston pin in the piston contact areas.
    Fig 2: Measuring Piston Pin Bore To Piston Pin Clearances
    G01815184Courtesy of GENERAL MOTORS CORP.
  3. Using an inside micrometer, measure the piston pin bore.
    4. Fig 3: Measuring Piston Pin Bore
    G01815185Courtesy of GENERAL MOTORS CORP.
  4. Compare your result with the piston diameter and piston to cylinder bore clearance listed in the Engine Mechanical Specifications .
  5. If the clearance is excessive, determine which piece is out of specification and replace as necessary.
  6. You must replace the piston if any of its dimensions are out of specification. There are no oversized pistons available.
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