Connecting Rod Bearing Clearance Measurement Procedure

Important:  Connecting rod bearings that have been used in a running engine, must be replaced with NEW connecting rod bearings for reassembly.

1. Before final assembly it is important to check the clearance of the new connecting rod bearings.
2. Place a length of fresh, room temperature plastic gaging material all the way across all the connecting rod bearing journal.
3. Install the connecting rod end cap on its original connecting rod making sure the bearing lock tangs are aligned on the same side of the rod.
   Fig 1: Installing Connecting Rod End Cap

   Courtesy of GENERAL MOTORS CORP.
4. When properly installed, the connecting rod bearing cap notches should be paired, as shown, on the crankpin.
   Fig 2: Identifying Connecting Rod Markings

   Courtesy of GENERAL MOTORS CORP.
   CAUTION: Refer to FASTENER NOTICE in Cautions and Notices.

   Important:  Reuse the old connecting rod bolts ONLY for measuring the connecting rod bearing clearance.

5. Lubricate connecting rod bolts with engine oil and install in the connecting rod.

   Tighten 

   Tighten the connecting rod bolts to 30 N.m (22 ft lbs).

6. Loosen the connecting rod bolts until the torque reading is zero.
7. Re-tighten the connecting rod bolts.
   1. 7.1. First Pass

      Tighten 

      Tighten the connecting rod bolts to 25 N.m (18 ft lbs).

   2. 7.2. Final Pass

      Tighten 

      Tighten the connecting rod bolts an additional 110 degrees using the J 36660-A. 

   Fig 3: Installing Connecting Rod End Cap

   Courtesy of GENERAL MOTORS CORP.
8. Allow the assembly to sit for at least two minutes,
9. Remove the connecting rod cap bolts.
10. Remove the connecting rod cap.
    Fig 4: Removing Connecting Rod End Cap

    Courtesy of GENERAL MOTORS CORP.
11. Determine the connecting rod bearing clearance by comparing the width of the flattened plastic gaging material at its widest point with the graduation on the gaging material container.
12. Compare the measurements with the engine mechanical specifications. Refer to Engine Mechanical Specifications  .
13. If the new bearings do not provide the proper crankshaft to bearing clearance, re-measure the crankshaft journals for the correct specified size and check to make sure you have the correct new bearings. If the crankshaft journals are incorrectly sized, replace the crankshaft. No crankshaft machining is permitted and undersized bearings are not available.
14. Clean the plastic gaging material from the connecting rod bearing and crankshaft connecting rod bearing journal using a soft lint-free cloth.
    Fig 5: Determining Connecting Rod Bearing Clearance

    Courtesy of GENERAL MOTORS CORP.