Piston Selection

WARNING: This page is about a different car, the 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 Chevrolet TrailBlazer, and 2004 Buick Rainier. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Measuring Piston Outside Diameter Using Micrometer

Courtesy of GENERAL MOTORS CORP.

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, pin, and connecting rod assembly may be installed if, after inspection is within specifications.

With a micrometer at a right angle, measure the piston outside diameter (OD). Measure the diameter 43 mm (1.69 in) from the top of the piston. Refer to Engine Mechanical Specifications .
Record the piston OD.

Fig 2: Measuring Bore Gauge With Micrometer

Courtesy of GENERAL MOTORS CORP.

Adjust the micrometer to the recorded piston OD.
Insert the J 8087 into the micrometer and zero the gage dial.

Fig 3: Measuring Cylinder Bore

Courtesy of GENERAL MOTORS CORP.

Using the J 8087 , measure the cylinder bore inside diameter (ID). Measure at a point 64 mm (2.5 in) from the top of the cylinder.
Record the cylinder bore ID.
Subtract the piston OD from the cylinder bore ID to determine the piston-to-bore clearance. Refer to Engine Mechanical Specifications .
If the proper clearance cannot be obtained, select another piston, pin, and connecting rod assembly and again measure the clearances. If the proper fit cannot be obtained, the cylinder bore may require honing for an oversize piston.