Piston Selection

WARNING: This page is about a different variant/trim than selected.

Fig 1: Bore Gauge

Courtesy of GENERAL MOTORS COMPANY

NOTE: 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.
Use a bore gauge (1) and measure the cylinder bore diameter. Measure at a point 62 mm (2.44 in) from the top of the cylinder bore.
Measure the bore gauge (1) with a micrometer (2) and record the reading.

Fig 2: Measuring Bore Gauge With A Micrometer
Courtesy of GENERAL MOTORS COMPANY
With a micrometer (2) or caliper at a right angle to the piston, measure the piston (1) 10 mm (0.3937 in) from the bottom of the skirt.

Fig 3: Outside Micrometer And Piston
Courtesy of GENERAL MOTORS COMPANY
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 clearances.
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 .