Fitting Pistons Service
- To determine if piston-to-cylinder clearance is within specification, piston skirt diameter must be measured at 90-degree angle to piston pin.
- Piston diameter is measured .45" (11.4 mm) for Metro or .60" (15.2 mm) for Metro LSi from bottom of piston skirt. Different size standard pistons are used. Piston size can be identified by No. 1 or No. 2 stamped on top of piston. See Fig 1.
- Piston diameter must be within specification. See PISTONS, PINS & RINGS SPECS TABLE at end of article.
- Cylinder bore diameter is measured at 1.96" (49.8 mm) and 3.74" (94.9 mm) from top of cylinder bore. Different cylinder bores are used and can be identified by No. 1 or No. 2 stamped on deck surface in accordance with cylinder location. See Fig 1.
- Cylinder bore diameter must be within specification. Determine piston clearance. Replace piston or rebore cylinder block if clearance is not within specification. See CYLINDER BLOCK SPECS TABLE at end of article.
Courtesy of GENERAL MOTORS CORP.