Pontiac Fiero 1984-1988 Repair Guide

Connecting Rod Bearings

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If you have already removed the connecting rod and piston assemblies from the engine, follow only Steps 3-7 of the following procedure.

REMOVAL, INSPECTION & INSTALLATION





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Fig. Fig. 1 Use a feeler gauge to check connecting rod side clearance



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Fig. Fig. 2 Check the bearing insert size markings to ensure you are installing the proper size replacement bearings



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Fig. Fig. 3 Compare the reading on the plastigage® package scale to the crankshaft specifications chart to check for proper bearing clearance



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Fig. Fig. 4 Apply a strip of gauging material to the bearing journal, then install and torque the cap



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Fig. Fig. 5 After the cap is removed again, use the scale supplied with the gauge material to check clearances

The connecting rod bearings are designed to have a slight projection above the rod and cap faces to insure a positive contact. The bearings can be replaced without removing the rod and piston assemblies from the engine.


CAUTION
The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

  1. Drain the engine oil and remove the oil pan. See the Oil Pan removal procedures. It may be necessary to remove the oil pump to provide access to rear connecting rod bearings.
  2.  
  3. With the connecting rod journal at the bottom of the travel, stamp the cylinder number on the machined surfaces of the connecting rod and cap for identification when installing, then remove the rod nuts and caps.
  4.  
  5. Inspect journals for roughness and wear. Slight roughness may be removed with a fine grit polishing cloth saturated with engine oil. Burrs may be removed with a fine oil stone by moving the stone on the journal circumference. Do not move the stone back and forth across the journal. If the journals are scored or ridged, the crankshaft must be reconditioned or replaced.
  6.  
  7. The connecting rod journals should be checked for out-of-round and correct size with a micrometer.
  8.  

Crankshaft rod journals will normally be standard size. If any undersized bearings are used, all will be 0.25mm undersize and 0.25mm will be stamped on the number 4 counterweight.

If Plastigage® material is to be used:

  1. Clean oil from the journal bearing cap, connecting rod and outer and inner surfaces of the bearing inserts. Position the insert so that the tang is properly aligned with the notch in the rod and cap.
  2.  
  3. Place a piece of Plastigage® material in the center of lower bearing shell as shown in the illustration.
  4.  
  5. Install the bearing cap onto the connecting rod and torque to specifications. Remove the bearing cap and determine the bearing clearances by comparing the width of the flattened plastic gauging material at its widest point with the graduation on the plastigage® package. The number within the graduation on the envelope indicates the clearance in thousandths of an inch or millimeters. If this clearance is excessive, replace the bearing and recheck the clearance with the plastigage® material. Lubricate the bearing with Assembly Lube or engine oil before installation. Repeat Steps 2-7 on the remaining connecting rod bearings.
  6.  

All rods must be connected to their journals when rotating the crankshaft, to prevent engine damage.

 
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