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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1670 (Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L - Repair Instructions - Off Vehicle (2 Of 3)) >> Piston, Connecting Rod, and Bearing Installation (L9H and L94) >> Piston Selection

Piston Selection

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    Fig 1: Identifying Piston Design
    GM2399938Courtesy of GENERAL MOTORS CORP.
    NOTE: 2010 Model Year: RPO's L9H and L94 have 1st and 2nd design piston and ring assemblies. If piston and/or ring assemblies are being replaced, design level must be identified for proper replacement.
  1. 1st design pistons have a cast dimple (1) on top of the piston 14.5 mm (a) inboard from outside edge.
  2. 2nd design pistons have a cast dimple (2) on top of the piston 5.5 mm (b) inboard from outside edge.
    3. Fig 2: Measuring Piston Outside Diameter
    GM1552496Courtesy of GENERAL MOTORS CORP.
    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, pin, and connecting rod assembly may be installed if, after inspection is within specifications.
  3. 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 (RPO L20 VIN A) or Engine Mechanical Specifications (RPO L96 VIN G) or Engine Mechanical Specifications (RPO L9H) or Engine Mechanical Specifications (RPO LC9 VIN 3) or Engine Mechanical Specifications (RPO LMG VIN 0) or Engine Mechanical Specifications (RPO LY6 VIN K) .
  4. Record the piston OD.
    5. Fig 3: Measuring Bore Gauge With Micrometer
    GM4974Courtesy of GENERAL MOTORS CORP.
  5. Adjust the micrometer to the recorded piston OD.
  6. Insert the J 8087:  bore gauge into the micrometer and zero the gauge dial.
    7. Fig 4: Measuring Cylinder Bore
    GM4972Courtesy of GENERAL MOTORS CORP.
  7. Using the J 8087:  bore gauge, measure the cylinder bore inside diameter (ID). Measure at a point 64 mm (2.5 in) from the top of the cylinder.
  8. Record the cylinder bore ID.
  9. Subtract the piston OD from the cylinder bore ID in order to determine the piston-to-bore clearance. Refer to Engine Mechanical Specifications (RPO L20 VIN A) or Engine Mechanical Specifications (RPO L96 VIN G) or Engine Mechanical Specifications (RPO L9H) or Engine Mechanical Specifications (RPO LC9 VIN 3) or Engine Mechanical Specifications (RPO LMG VIN 0) or Engine Mechanical Specifications (RPO LY6 VIN K) .
  10. If the proper clearance cannot be obtained, select another piston and pin assembly and measure the clearances again. If the proper fit cannot be obtained, the cylinder bore may require honing for an oversize piston.
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