Cummins QSM Parts for Australia - Connecting Rod Section

Cummins QSM11 Connecting Rod Components & Bearings

The connecting rods of a Cummins QSM11 engine are among the most critical components in the internal combustion process. These rods transfer explosive force from the piston to the crankshaft and are exposed to intense mechanical stress, rapid acceleration, and high thermal cycling with every engine revolution. As a result, any failure in the connecting rod assembly—including the bearings—can result in catastrophic engine damage.

At Diesel Pro Power, we offer premium replacement connecting rod bearing sets for the Cummins QSM11, available in standard and oversize specifications. With over 40,000 satisfied customers, our parts are trusted by industrial operators, marine engineers, and rebuild specialists worldwide.

The Role of Connecting Rod Bearings in the QSM11

What Are Connecting Rod Bearings?

Connecting rod bearings in the Cummins QSM11 serve a critical role by:

• Providing a low-friction surface for the rod to rotate around the crankshaft journal
  
  

• Maintaining oil film separation between metal surfaces
  
  

• Accommodating the high loads during combustion and piston motion
  
  

• Preventing metal-to-metal contact and crankshaft scoring
  
  

The bearings are composed of soft metal alloys that can embed small contaminants and withstand minor alignment issues—making them the sacrificial surface during abnormal conditions.

Operating Environment

In a high-output engine like the QSM11, the bearings must endure:

• Peak firing pressures of over 2000 psi
  
  

• Continuous operating temperatures of 180°F to 220°F (or more in marine environments)
  
  

• Journal speeds exceeding 2,000 revolutions per minute under load
  
  

This makes proper selection, installation, and lubrication of the connecting rod bearings absolutely essential.

Connecting Rod Bearing Sets for Cummins QSM11

Standard Size Bearing Set

Our standard size connecting rod bearing set is designed for use with QSM11 engines that still operate within factory crankshaft specifications.

• Includes Upper and Lower Halves for one connecting rod journal
  
  

• Material: Tri-metal or bi-metal alloys, depending on OEM spec
  
  

• Coating: Often includes a lead-free overlay for extended wear resistance
  
  

• Machined for Precision Fitment and ideal oil film clearance
  
  

Used when rebuilding an engine with minimal crankshaft wear or during preventive maintenance inspections where journals mic within spec.

0.010" Oversize Bearing Set

Our 0.010” oversize (undercut) bearing set is designed for crankshafts that have been ground or polished due to wear or scoring.

• Allows for safe reuse of crankshafts with minor journal damage
  
  

• Requires proper machining to maintain concentricity and taper within limits
  
  

• Each set still includes upper and lower bearing halves for one connecting rod
  
  

Oversize bearings are a common requirement during mid-life or top-end rebuilds of QSM11 engines operating under high-hour, high-load conditions.

0.020" Oversize Bearing Set

For more severe crankshaft wear or regrinding:

• The 0.020" oversize bearing set allows a second service cut on the crankshaft
  
  

• Provides the same high-quality bearing surface as the standard size
  
  

• Still compatible with OEM connecting rods and fasteners
  
  

Using an oversize bearing does not compromise engine strength when installed properly. Instead, it restores reliable bearing clearances and oil film integrity.

Understanding Bearing Clearance in Cummins QSM11 Engines

Why Clearance Matters

Bearing clearance—the space between the bearing surface and the crankshaft journal—is critical to engine longevity. In the QSM11:

• Too little clearance = Insufficient oil film → Risk of bearing seizure
  
  

• Too much clearance = Loss of oil pressure → Reduced load support and increased wear
  
  

Diesel Pro Power recommends always measuring crankshaft journals with a micrometer and verifying against Cummins QSM11 factory specifications before selecting standard or oversize bearings.

Measuring with Plastigage

If you do not have access to precision micrometers, Plastigage can be used to confirm clearance:

1. Install bearing shell dry (no oil), torque to spec
   
   

2. Insert Plastigage across journal
   
   

3. Remove cap and compare width of squished material to the scale
   
   

This quick method confirms whether your existing crankshaft can accept a standard, 0.010", or 0.020" bearing set.

When to Replace QSM11 Connecting Rod Bearings

Scheduled Rebuilds

For marine, industrial, or generator-set applications, Cummins QSM11 engines are often overhauled at predictable intervals (e.g., 15,000 to 25,000 hours). Replacing rod bearings during these intervals ensures:

• Prevention of spun bearings
  
  

• Avoidance of crankshaft scoring
  
  

• Restoration of oil pressure consistency
  
  

Signs of Bearing Wear or Damage

• Knocking or thudding noise under load
  
  

• Low oil pressure, particularly at idle
  
  

• Metal shavings found in oil filter or drain pan
  
  

• Excessive rod side clearance
  
  

If any of these symptoms are present, bearings should be inspected and replaced immediately.

Replacing Connecting Rod Bearings: Step-by-Step

Note: This is a general overview. Always follow Cummins service manual torque specs and procedures.

1. Drain Oil & Remove Pan – Access bottom end of the engine.
   
   

2. Inspect Journals – Use micrometer to measure crankshaft for scoring, taper, or out-of-round condition.
   
   

3. Remove Rod Cap – Mark orientation to ensure reinstall in same direction.
   
   

4. Replace Bearings – Install upper and lower halves, making sure oil hole alignment is correct.
   
   

5. Torque Rod Bolts – Typically in multiple stages using a stretch gauge or torque-to-yield method.
   
   

6. Check Rotation – Rod should move smoothly on crankshaft without binding.
   
   

7. Reassemble Engine – Use new gaskets and torque specs throughout reinstallation.
   
   

Connecting Rod Reuse Guidelines

Cummins QSM11 connecting rods are forged steel and can typically be reused unless:

• Bent or twisted
  
  

• Surface pitting on big-end bore
  
  

• Bushing in small end worn or cracked
  
  

• Bolt threads stretched or damaged
  
  

Always inspect connecting rod bolts and consider replacing them during major rebuilds.

Common Mistakes to Avoid

• Mixing bearing halves from different sets
  
  

• Improper torqueing of rod bolts (leading to bearing crush issues)
  
  

• Using standard bearings on undersized crankshafts
  
  

• Skipping journal inspection – even a 0.001" taper can lead to rapid failure
  
  

Other QSM11 Lower-End Components Often Replaced With Bearings

• Main bearings
  
  

• Thrust washers
  
  

• Rod bolts
  
  

• Oil pump
  
  

• Oil cooler
  
  

• Lower gasket set
  
  

At Diesel Pro Power, we stock all of these components and can help you build a complete bottom-end kit tailored to your QSM11 configuration.

Why Buy from Diesel Pro Power?

• Precision-Matched Sets – Every bearing set is matched for proper sizing and coating type.
  
  

• Global Shipping – Trusted by customers in over 100 countries.
  
  

• Fast Order Fulfillment – In-stock items ship same day.
  
  

• Spanish-Speaking Support Available – Hablamos Español.
  
  

• Expert Guidance – Not sure if you need oversize bearings? We’ll help you identify the right fit.