Piston Selection

Tools Required: 

• J 8087  Cylinder Bore Gauge
• J 36660-A  Torque Angle Meter
• J 8037  Piston Ring Compressor

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

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

A used piston and pin set may be reinstalled if, after cleaning and inspection, they are within specifications.

1. Inspect the engine block cylinder bore. Refer to Engine Block - Cleaning & Inspection .
2. Inspect the piston and the piston pin. Refer to Piston, Connecting Rod & Bearings - Cleaning & Inspection .
3. Use the J 8087  to measure the cylinder bore diameter. Measure at a point 64 mm (2.5 in) from the top of the cylinder bore.
   Fig 1: Measuring Cylinder Bore Diameter

   Courtesy of GENERAL MOTORS CORP.
4. Measure the J 8087  with a micrometer and record the reading.
   Fig 2: Measuring Cylinder Bore Gauge

   Courtesy of GENERAL MOTORS CORP.
5. With a micrometer or caliper at a right angle to the piston, measure the piston 42 mm (1.65 in) from the top of the piston.
6. Subtract the piston diameter from the cylinder bore diameter in order to determine piston-to-bore clearance.
7. For proper piston-to-bore clearance. Refer to Engine Mechanical Specifications .
8. If the proper clearance cannot be obtained, select another piston and measure for the clearances.
9. If the proper fit cannot be obtained, hone the cylinder bore or replace the cylinder block.
10. When the piston-to-cylinder bore clearance is within specifications, mark the top of the piston using a permanent marker for installation to the proper cylinder. Refer to Separating Parts .
    Fig 3: Measuring Piston

    Courtesy of GENERAL MOTORS CORP.