Connecting Rods And Rod Bearings

Replacement and Installation Guide

Time Required:

3 hours

Tools Needed:

• Standard socket set
• Rubber mallet
• Crankshaft socket
• Breaker bar
• Feeler gauge

Cost:

Approximately $50 for bearings and supplies

Parts and Materials:

• Quality set of rod bearings
• Plastigage
• 3/8" rubber hose

Tip:

To avoid scratching or damaging the cylinder walls when removing or installing pistons and rod assemblies, cut two short lengths of 3/8" rubber hose and slide them over the rod bolts.

Performance Gains:

Ensures smooth, reliable operation of the engine's lower rotating assembly.

Preparation

Rebuilding an engine requires time, attention to detail, and plenty of space. Start by clearing out your garage for an organized and efficient workspace.

1. Degrease and Mount the Engine:
   Thoroughly clean the motor and secure it on a sturdy, rotation-style engine stand for easy access.

2. Disassemble the Engine:

   • Remove the intake manifold and cylinder heads.
   • Drain the engine oil before flipping the engine block over.

3. Access the Rotating Assembly:

   • Remove the oil pan and retain the bolts in labeled bags.
   • Remove the oil pump and extension shaft for added clearance.

Removing the Connecting Rods

1. Label Components:

   • Mark each rod and cap with its respective cylinder number using a scribe.
   • Ensure the cap orientation is marked for proper reinstallation.

2. Loosen and Remove:

   • Loosen and remove the rod bearing caps from the crankshaft.
   • Carefully slide the rod assemblies out of the cylinder bores. Use clean engine oil to coat the cylinder walls and a mallet to gently tap the rods if needed.

Inspecting the Rod Bearings

1. Check for Wear:

   • Inspect the bearing surfaces for flaking or scoring. Replace any bearings showing excessive wear.

2. Check Clearance:

   • Use Plastigage to measure rod-to-crankshaft bearing clearance:
     • Clean the bearing shell and crank journal.
     • Place a strip of Plastigage along the lower bearing shell.
     • Install the cap and torque to specifications.
     • Remove the cap and measure the flattened Plastigage with the included scale.
     • Verify the clearance against manufacturer specifications.

3. Crankshaft Inspection:

   • Inspect for ridging or damage on the crankshaft journals. If damaged, replace or regrind the crankshaft and use undersized bearings.

Installing New Rod Bearings

1. Prepare the Bearings:

   • Install the new bearings into the rods and caps. Ensure the ends extend slightly beyond the surfaces to seat properly when tightened.

2. Reinstallation:

   • Coat the new bearings, cylinder walls, and crank journals with clean engine oil.
   • Insert the rod assemblies back into their respective cylinders.
   • Ensure the notches on the pistons face the front of the engine.

3. Final Assembly:

   • Loosely fit the rod bearing caps onto the crank journals.
   • Check the clearance between the rods and the crankshaft using a feeler gauge. Ensure everything is within factory specifications.

Completion

1. Reinstall the oil pump and pan.
2. Tighten all hardware to the manufacturer’s torque specifications.

Helpful Resources

There are numerous useful videos on YouTube for replacing rod bearings and connecting rods. Watching these alongside this guide can provide additional clarity and confidence.