GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 GMC Suburban - 4WD 🢒 Engine 🢒 Engine Mechanical - 7.4L 🢒 Piston and Connecting Rod Inspection

Cleaning Procedure
  1. Remove all varnish and carbon deposits. Do not use a wire brush.
  2. Use an approved cleaning solution in order to remove the carbon build-up.
  3. Remove the carbon from the ring grooves. Use a ring groove cleaning tool.
  4. Clean the oil-control ring groove holes.

Inspection Procedure
  1. Inspect the piston pin bore and the connecting rod bore for scuffing and burrs.
  2. Inspect the connecting rod for damage. If a suitable jig is available, check the connecting rod for a bent or twisted condition.
  3. Inspect the piston components for the following conditions:
    4. • Scratches, scuffing, and burrs
    • The ring land for cracking and wear.
    • The ring grooves for burrs and nicks.
    • The skirts and the pin bosses for cracking.
    • The skirts for scuffing.
  4. Inspect the connecting rod bearings for scratches or deep pitting.

Measuring Procedure

    Object Number: 4976 Size: SH
  1. Measure the piston pin diameter. Refer to Engine Mechanical Specifications .

    2. Object Number: 4975 Size: SH
  2. Measure the piston pin to piston clearance as follows:
    3. 2.1. Measure the piston pin hole diameter.
    2.2. Subtract the piston pin diameter from the piston pin hole diameter in order to obtain the clearance.
    2.3. Replace the piston and the piston pin if the clearance exceeds the specifications. The piston and the piston pin are a matched set and not available separately.