Piston Selection

WARNING: This page is about a different car, the 2003 Pontiac Sunfire and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

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.

Inspect the engine block cylinder bore. Refer to Engine Block Cleaning and Inspection .
Inspect the piston and the piston pin. Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection .
Use a bore gauge and 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.
Measure the bore gauge with a micrometer and record the reading.

Fig 2: Measuring Bore Gauge
Courtesy of GENERAL MOTORS CORP.
With a micrometer or caliper at a right angle to the piston, measure the piston 14 mm (0.570 in) from the bottom of the skirt.

Fig 3: Measuring Piston Width
Courtesy of GENERAL MOTORS CORP.
Subtract the piston diameter from the cylinder bore diameter in order to determine piston-to-bore clearance.
For proper piston-to-bore clearance. Refer to ENGINE MECHANICAL SPECIFICATIONS .
If the proper clearance cannot be obtained, select another piston and measure for the clearance.
If the proper fit cannot be obtained, hone the cylinder bore or replace the cylinder block.
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 .