Cummins ISB 5.9L Engine Parts – Connecting Rod Components

The connecting rod assembly is a critical component in the Cummins ISB 5.9L engine, responsible for transferring combustion force from the piston to the crankshaft. A well-maintained connecting rod system ensures smooth operation, optimal power output, and long-term engine reliability.
This section details all connecting rod–related components available for the Cummins ISB 5.9L, including bearing sets, bushings, and cap bolts for both fractured and non-fractured rod designs. All parts are manufactured to precise Cummins specifications, ensuring a perfect fit and OEM-level performance.

Connecting Rod Bearing Sets for Cummins ISB 5.9L

Standard Size Bearing Sets – Non-Fractured Connecting Rods

These bearing sets are designed to service a single connecting rod in Cummins ISB 5.9L engines equipped with non-fractured rods.

• Includes both upper and lower bearing shells.

• Manufactured for standard crankshaft journal dimensions.

• Engineered to deliver optimal oil clearance and prevent premature wear.

• Compatible with earlier B-series applications including 4B, 4BT, and 6B models.

Oversize Bearing Sets – Non-Fractured Connecting Rods

When crankshaft journals are reground during an overhaul, an oversize bearing set is required to restore correct clearance. Available in two oversize dimensions:

• 0.25 mm Oversize: Designed for journals ground down by 0.25 mm.

• 0.50 mm Oversize: Designed for journals ground down by 0.50 mm.
  These bearings feature precision-machined surfaces for consistent oil film strength and reduced friction.

Standard Size Bearing Sets – Fractured Connecting Rods

For Cummins ISB 5.9L engines equipped with fracture-split rods, this standard size bearing set includes both upper and lower halves for one rod.

• Hardened steel backing for strength.

• Tri-metal construction for superior load capacity.

• Ideal for direct replacement without machining crankshaft journals.

Oversize Bearing Sets – Fractured Connecting Rods

Oversize bearing sets for fractured connecting rods are available in:

• 0.25 mm Oversize

• 0.50 mm Oversize
  These bearings are engineered to provide optimal fit after crankshaft regrinding, ensuring smooth journal rotation and preventing metal-to-metal contact.

Connecting Rod Bushings for Cummins ISB 5.9L

The connecting rod bushing serves as the bearing surface for the piston pin, enabling smooth pivoting between the connecting rod and piston.

• Made from high-strength alloy materials for maximum wear resistance.

• Precision-machined to maintain exact clearance for the piston pin.

• Suitable for both fractured and non-fractured rod styles in Cummins ISB 5.9L, 4BT, 6BT, and QSB engines.

Regular inspection of connecting rod bushings is recommended during any top-end rebuild to prevent piston pin scoring and uneven wear.

Connecting Rod Cap Bolts for Cummins ISB 5.9L

Early-Style Cap Bolts for Non-Fractured Rods

Designed for use with non-fractured connecting rods, these bolts secure the connecting rod cap to the rod body.

• High tensile strength to withstand combustion pressures.

• Thread design ensures proper torque retention.

• Should always be replaced when removed to maintain clamping force.

Cap Bolts for Fracture-Split Connecting Rods

These bolts are specifically engineered for the unique clamping requirements of fractured connecting rods used in modern Cummins ISB 5.9L engines.

• Precision-threaded for exact fit.

• Heat-treated for enhanced durability.

• Recommended replacement during any bottom-end rebuild.

Importance of Choosing the Correct Connecting Rod Components

The Cummins ISB 5.9L engine uses both fractured and non-fractured rod designs depending on production year and application. Identifying the correct type is essential for selecting the right bearing sets, bushings, and cap bolts. Using incorrect components can lead to:

• Improper oil clearance

• Premature bearing failure

• Excessive vibration

• Potential connecting rod failure

Always verify rod style before ordering parts. If the rod has a smooth mating surface between the cap and body, it is a non-fractured type. If the mating surface appears irregular or jagged, it is a fracture-split rod.

Maintenance and Replacement Guidelines

• Bearing Clearance Checks: Measure clearance using plastigage during installation to confirm specifications.

• Cap Bolt Torque: Always follow Cummins torque specifications and use new bolts during reassembly.

• Bushing Replacement: Replace bushings if scoring, excessive wear, or out-of-round conditions are detected.

• Lubrication: Use assembly lube on all bearing surfaces during installation to prevent dry start damage.