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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 596 (Engine Mechanical - 3.5L (Unit Repair)) >> Repair Instructions >> Piston, Connecting Rod, and Bearings Cleaning and Inspection >> Piston Ring Measurement

Piston Ring 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 the piston ring end gap using the following procedure:
    1. 1.1. Place the piston ring in the area of the bore where the piston ring will travel, approximately 25 mm (1 in) down from the deck surface. Ensure that the ring is square with the cylinder bore by positioning the ring with the piston head.
    2. 1.2. Measure the end gap of the piston ring with feeler gages. Refer to Engine Mechanical Specifications .
    3. 1.3. If the clearance exceeds the provided specifications, the piston rings must be replaced.
    4. 1.4. Repeat the procedure for all the piston rings.
    Fig 1: Measuring Piston Ring End Gap
    G01815186Courtesy of GENERAL MOTORS CORP.
  2. Measure the piston ring side clearance using the following procedure:
    1. 2.1. Roll the piston ring 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.
    2. 2.2. With the piston ring on the piston, use feeler gages to check clearance at multiple locations.
    3. 2.3. Compare the measurements with piston ring side clearance listed in the Engine Mechanical Specifications .
    4. 2.4. If the clearance is greater than specifications, replace the piston rings.
    Fig 2: Measuring Piston Ring Side Clearance
    G01815187Courtesy of GENERAL MOTORS CORP.
  3. When replacing the piston rings, only install re-ring sets that have a 1.2 mm (0.0472 in) thick steel upper compression ring and multi-piece oil rings. The top compression ring may be installed with either side up. There is a locating dimple (1) on the 2nd compression ring near the end for identification of the top side. Install the 2nd compression ring with the dimple facing up.
  4. If the new ring does not reduce the clearance to the proper specification, install a new piston.
    Fig 3: Identifying Locating Dimple
    G01815188Courtesy of GENERAL MOTORS CORP.
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