Piston Selection

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

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

A use piston and piston pin set may be reinstalled if, after clearing and inspection, the piston and piston pin are within specifications.

1. Use the J 8087  in order to measure the cylinder bore diameter. Measure at a point 64 mm (2.5 in) from the top of the cylinder bore and 90 degrees to the crankshaft centerline.
   Fig 1: Measuring Cylinder Bore Diameter

   Courtesy of GENERAL MOTORS CORP.
2. Measure the J 8087  with a micrometer and record the reading.
   Fig 2: Measuring J 8087 With Micrometer And Record Reading

   Courtesy of GENERAL MOTORS CORP.
3. With a micrometer or caliper or a right angle to the piston pin bore, measure the piston 11 mm (0.433 in) from the bottom of the skirt.
   Fig 3: Installing Proper Cylinder

   Courtesy of GENERAL MOTORS CORP.
4. Subtract the piston diameter from the cylinder bore diameter in order to determine piston-to-bore clearance. Refer to ENGINE MECHANICAL SPECIFICATIONS  .
5. If the proper clearance cannot be obtained, then defect another piston and measure the clearances.

   If the proper it cannot be obtained, the cylinder bore may require honing or boring.

6. When the piston-to-cylinder bore clearance is within specifications, permanently mark the top of the piston for installation into the proper cylinder.