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ROD BEARING REPLACEMENT

Fig. 1: Checking the ring-to-ring groove clearance

Fig. 2: The notch on the the side of the bearing cap matches the groove on the bearing insert

Fig. 3: Inspect the rod bearings for scuffing or other wear — also check the crankshaft journal

Fig. 4: Measure the connecting rod length at these points

Fig. 5: Measuring the connecting rod bearing oil clearance with a strip of Plastigage® material

Fig. 6: Apply a strip of gauging material to the bearing journal, then install and torque the cap

Fig. 7: 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.

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

  1. Remove the oil pan. See the Oil Pan procedures, earlier in this section.
  2. With the connecting rod journal at the bottom, stamp the cylinder number on the machined surfaces of the connecting rod and cap for identification when installing, then remove the caps.
  3. 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 replaced.
  4. The connecting rod journals should be checked for out-of-round and correct size with a micrometer.

    NOTE: 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 plastic gauging material is to be used:

  5. 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.
  6. Place a piece of plastic gauging material in the center of lower bearing shell.
  7. 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 container. 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 plastic gauging material. Undersized bearings are available in sizes of 0.25mm, 0.50mm and 0.75mm. Lubricate the bearing with engine oil before installation. Repeat Steps 2–7 on the remaining connecting rod bearings. All rods must be connected to their journals when rotating the crankshaft, to prevent engine damage.

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