Crankshaft & Parts

The Genuine Porsche Connecting Rod Bush (Part Number: 9A110312202) is a precision-engineered internal engine component designed to provide a durable, low-friction bearing surface between the connecting rod small end and the piston pin on selected Porsche 911, Boxster and Cayman engines.
Sold Each.
x6 Required Per Car.

Fits:

• Porsche Boxster 987 MKII 2.9L 2009-12
• Porsche Boxster S 987 MKII 3.4L 2009-12
• Porsche 997 MKII Carrera C2 3.6L 2009-12
• Porsche 997 MKII Carrera C4 3.6L 2009-12
• Porsche 997 MKII Carrera C2S 3.8L 2009-12
• Porsche 997 MKII Carrera C4S 3.8L 2009-12
• Porsche Cayman 2.9L 987C MKII 2009-12
• Porsche Cayman S / R 3.4L 987C MKII 2009-12  

The connecting rod bush is installed within the small end of the connecting rod, providing a precisely fitted bearing surface that allows the piston pin to articulate smoothly as the piston moves up and down inside the cylinder.

Maintaining the correct clearance between the connecting rod bush and piston pin is essential for smooth engine operation, efficient power transfer and long-term internal engine reliability.

Over time, connecting rod bushes can become worn, scored or damaged due to inadequate lubrication, excessive mechanical loading, overheating or prolonged engine operation. Excessive clearance can result in unwanted engine noise, increased vibration and accelerated wear of the piston pin and connecting rod assembly.

Replacing a worn or damaged connecting rod bush with a Genuine Porsche component helps restore the correct bearing clearance and maintain reliable operation of the engine's reciprocating assembly.

Ideal for professional engine rebuilding, connecting rod refurbishment and internal engine repairs, this Genuine Porsche connecting rod bush provides the correct replacement specification for compatible Porsche engines.

What This Product Does:
The connecting rod bush, also known as a small-end bush or piston pin bush, is an essential component within the engine's piston and connecting rod assembly.

Its primary function is to provide a low-friction bearing surface between the small end of the connecting rod and the piston pin, also known as the gudgeon pin or wrist pin.

During engine operation, combustion forces push the piston downwards within the cylinder. These forces are transferred through the piston pin and connecting rod to the crankshaft, converting the piston's reciprocating movement into rotational motion.

The connecting rod bush allows controlled relative movement between the piston pin and connecting rod while maintaining the precise clearance required for reliable operation.

Its main functions include:

• Reducing friction: Provides a low-friction bearing surface between the piston pin and connecting rod small end.
• Supporting smooth piston movement: Allows the piston pin to articulate correctly as the connecting rod changes angle during engine operation.
• Maintaining correct bearing clearance: Helps preserve the precise mechanical tolerances required between the piston pin and connecting rod.
• Distributing mechanical loads: Transfers combustion and inertial forces across the bearing contact surface.
• Protecting the connecting rod: Reduces direct metal-to-metal wear between the piston pin and connecting rod bore.
• Supporting engine reliability: Helps maintain dependable operation of the reciprocating assembly under demanding engine loads.
• Reducing mechanical noise: Correct bearing clearances help minimise unwanted movement and knocking associated with excessive small-end wear.
• Supporting efficient power transfer: Maintains the mechanical connection that transfers piston forces through the connecting rod to the crankshaft.

Although designed for long service life, the bushes may deteriorate due to lubrication problems, excessive temperatures, contamination, high engine loads or incorrect assembly clearances.

Common symptoms of a worn or failing connecting rod bush include:

• Engine knocking or tapping noises: Excessive clearance between the piston pin and connecting rod bush may produce a metallic tapping or knocking sound during engine operation.
• Unusual engine noise during acceleration: Changes in combustion load may make excessive small-end clearance more noticeable.
• Increased mechanical vibration: Severe wear may contribute to abnormal movement within the piston and connecting rod assembly.
• Excessive piston pin clearance: A worn bush may allow movement beyond the manufacturer's specified tolerance.
• Scoring or surface damage: Inspection during engine dismantling may reveal scratches, scoring or wear marks on the internal bearing surface.
• Discolouration or overheating damage: Insufficient lubrication or excessive friction can cause heat-related damage to the bush and piston pin.
• Uneven bearing wear: Incorrect alignment, lubrication problems or excessive loading may produce irregular wear patterns.
• Metallic particles in engine oil: Severe internal wear may introduce metallic debris into the lubrication system.
• Damage to the piston pin: Excessive bush wear may cause scoring or deterioration of the corresponding piston pin surface.
• Reduced engine reliability: Continued operation with excessive small-end clearance may increase the risk of further damage to the piston and connecting rod assembly.

A deteriorated bush may develop excessive clearance around the piston pin, allowing unwanted movement and increasing contact stresses within the connecting rod small end.

If left unresolved, this wear may result in abnormal engine noise, damage to the piston pin, accelerated wear of surrounding components and potentially serious internal engine damage.

Installing a Genuine Porsche replacement connecting rod bush helps to:

• Restore correct bearing clearance: Maintain the precise fit required between the piston pin and connecting rod small end.
• Reduce unwanted mechanical movement: Eliminate excessive play caused by a worn bush when correctly fitted and machined.
• Protect the piston pin: Provide a renewed bearing surface to reduce friction and prevent further pin damage.
• Support smooth engine operation: Maintain controlled movement within the piston and connecting rod assembly.
• Improve internal engine reliability: Replace worn bearing surfaces before further mechanical damage develops.
• Maintain efficient force transfer: Preserve the mechanical connection between the piston and crankshaft.
• Reduce the risk of engine damage: Prevent continued operation with excessive small-end clearance that could damage associated components.
• Support professional engine rebuilding: Provide a replacement bearing component during connecting rod refurbishment.
• Preserve original Porsche specifications: Restore the intended dimensions and mechanical characteristics when correctly installed.
• Maintain long-term durability: Support reliable operation under the high loads experienced in Porsche flat-six engines.

Replacing connecting rod bushes is particularly recommended during engine rebuilding when inspection identifies excessive clearance, scoring, deformation or other damage.

Because these components are located inside the engine, replacement generally requires significant engine disassembly and specialist machining procedures.

Crankshaft pulleys like this one are designed to last the engine's lifetime, but here are the common failure modes to watch for: 

• Rubber deterioration or separation causing excessive vibrations 
• When the vibration damper fails, crankshaft vibrations aren’t absorbed, leading to noticeable engine shake—especially at certain RPMs—which can damage internal components and accessories. 
• Noisy operation or belt misalignment. A failing pulley may cause the belt to slap or misalign, resulting in rubbing noises or excessive wear. 
• Battery warning light or charging glitch. If the pulley fails and stops turning the alternator belt, the battery light may illuminate due to loss of charging. 

Diagram Ref No 6