nut Genuine Porsche part 99310317403

Con Rod Nut 
Sold each - 12 required per car

The OE Match Con Rod Nut is a critical internal engine fastener used to secure the connecting rod cap to the connecting rod assembly. Suitable for various Porsche 911, 964, 993, 996 Turbo and 997 Turbo engines, this precision-engineered component plays a vital role in maintaining the structural integrity of the engine's rotating assembly.

Fits:

• Porsche 911 1984-1986 3.2L
• Porsche 911 1987-1989 3.2L G50
• Porsche 911 1978-1989 3.3L Turbo (930)
• Porsche 964 (911) C2 1989-93
• Porsche 964 (911) C4 1989-93
• Porsche 964 (911) RS 3.6L 1991-93
• Porsche 964 (911) RS 3.8L 1991-93
• Porsche 964 (911) TURBO 3.3L 1991-93
• Porsche 964 (911) TURBO 3.6L 1991-93
• Porsche 993 (911) C2 1994-97
• Porsche 993 (911) C4 1994-97
• Porsche 993 (911) RS 1994-97
• Porsche 993 (911) C2S 1994-97
• Porsche 993 (911) C4S 1994-97
• Porsche 993 (911) TURBO 1994-96
• Porsche 993 (911) GT2 1994-97
• Porsche 993 (911) TURBO S 1994-97
• Porsche 996 TURBO 2000-05
• Porsche 996 GT2 2001-05
• Porsche 997 MK1 TURBO 2007-09
• Porsche 997 MK1 GT2 2007-09

Diagram Ref No 11

The connecting rod assembly is subjected to enormous forces during engine operation, particularly at high RPM. The con rod nuts must maintain precise clamping force to ensure the connecting rod cap remains securely attached under extreme combustion and inertial loads. Even the slightest loss of clamping force can result in catastrophic engine failure.

For this reason, con rod nuts are considered a critical engine rebuild component and should always be replaced during engine overhauls, connecting rod servicing or performance engine builds.

What Does a Con Rod Nut Do?

The con rod nut secures the connecting rod cap to the connecting rod body, clamping around the crankshaft journal bearing.

Its functions include:

• Maintaining connecting rod cap security
• Preserving bearing crush and alignment
• Supporting crankshaft rotation
• Withstanding high engine loads
• Maintaining precise clamping force
• Supporting engine reliability
• Protecting internal engine components

The connecting rod assembly relies entirely on the integrity of its fastening hardware to survive the extreme loads generated during operation.

Why Do Con Rod Nuts Fail?

Con rod nuts are subjected to repeated tensile loads, heat cycles and vibration throughout their service life.

Common causes of failure include:

• Metal fatigue
• Repeated engine stress cycles
• Overstretching during previous installation
• Improper torque procedures
• High mileage wear
• Performance engine operation
• Corrosion during storage
• Reuse during multiple rebuilds

Many con rod nuts are designed as single-use fasteners and can lose their ability to maintain proper clamping force if reused.

When Should Con Rod Nuts Be Replaced?

Replacement is strongly recommended whenever the connecting rods are disassembled.

Typical situations include:

• Engine rebuilds
• Crankshaft replacement
• Connecting rod servicing
• Bearing replacement
• Performance engine upgrades
• Motorsport engine preparation
• Full engine restoration projects
• Preventative rebuild maintenance

As con rod nuts are relatively inexpensive compared to the cost of engine repairs, replacing them during rebuild work is considered essential best practice.

Why Replacement Matters

The con rod nut is one of the most critical fasteners within the entire engine.

Benefits of replacement include:

• Maintains correct clamping force
• Supports bearing integrity
• Reduces risk of engine failure
• Improves engine reliability
• Protects expensive internal components
• Essential for professional engine builds
• Supports high-performance applications
• Provides peace of mind during rebuilds

For air-cooled and turbocharged Porsche engines, correct connecting rod hardware is fundamental to long-term durability and performance.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99310317403

The product you are viewing cross references to these numbers

Big End Conrod Bearings. Standard size.
SET OF 12.

Fits:
Porsche 993 1994-98
Porsche 996 Turbo

Click picture for large parts diagram.
Diagram Ref No 15.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99310314715

The product you are viewing cross references to these numbers

Connection rod bolts M9 and nuts. SET OF 12.

Fits:
Porsche 911 3.2 (84-89)
Porsche 911 Turbo 3.3 (78-89)
Porsche 964 C2 (90-94)
Porsche 964 C4 (89-94)
Porsche 964 RS (92-92)
Porsche 964 Turbo-Look (91-94)
Porsche 964 CUP-RACE (90-93)
Porsche 964 Turbo 3.3 (91-92)
Porsche 964 Turbo 3.6 (93-94)
Porsche 993 C2
Porsche 993 C4
Porsche 993 C2S
Porsche 993 C4S
Porsche 993 RS
Porsche 993 Turbo
Porsche 993 Turbo S
Porsche 993 GT2

Click 'Zoom in' for large parts diagram.
Diagram Ref No 13

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

96410317605

The product you are viewing cross references to these numbers

OE Match big end conrod bearings for Porsche 993 and 996 Turbo applications, supplied as a SET OF 12 in the Oversize 0.25mm specification. These replacement shells are intended for correctly measured engine rebuilding work.

Fits

Porsche 993 1994-98

Check fitment for your specific vehicle (model, year, engine) before ordering.

Diagram ref no: 15

What This Product Does

The bearing shells sit within the connecting-rod big ends, forming the lubricated interface with the crankshaft journals. Correctly selected bearings support rod movement and distribute combustion loads while maintaining the oil clearance required by the engine specification.

Functions

• Provide a bearing surface between each connecting rod and its crankshaft journal.
• Support lubricated movement at the big-end connection.
• Distribute loads transmitted through the connecting rods.
  
  

Technical Details

• Brand: OE Match.
• Product reference retained from the supplied information: 71-3775/6.
• Connecting-rod bearing reference: 99310314753.
• Specification: Oversize 0.25mm.
• Contents: SET OF 12 bearing shells.
  
  

Symptoms of Fault

• A deep knock or rumble, particularly when the engine is loaded.
• Oil-pressure warnings or pressure falling as the engine warms.
• Metal particles discovered during oil or filter inspection.
• Scoring or uneven wear found on dismantled bearing surfaces.
  
  

These findings require diagnosis; none identifies a bearing fault conclusively on its own.

Why Replacement Matters

Renewing worn shells during an engine rebuild allows the builder to establish suitable bearing clearances and inspect the crankshaft and rods for associated damage. Any underlying lubrication problem, contamination or overheating must also be investigated rather than addressed by bearing replacement alone.

FAQs

Can these be selected by vehicle model alone?
No. The listed application must be checked alongside the measured crankshaft journals and the required bearing specification. Oversize 0.25mm must not be assumed suitable for every rebuild.

What needs checking before installation?
Inspect the journals and connecting rods, measure the assembled clearances and investigate the cause of existing wear. A competent engine builder should confirm the final selection.

Does low oil pressure always mean worn bearings?
No. It is a reason to investigate the lubrication system and internal condition, not proof that these shells require replacement.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99310314753

The product you are viewing cross references to these numbers

Connection rod nut.
12 per engine. Price is for each.

Fits:
Porsche 911 1984-89
Porsche 911 (930) Turbo 1978-89
Porsche 964 1989-94
Porsche 993 1994-98
Porsche 996 Turbo / GT2 1998-05
Porsche 997 Turbo / GT2 2005-08

Click 'Zoom in' for large parts diagram.
Diagram Ref No 11.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99310317403

The product you are viewing cross references to these numbers

Big end conrod bearings.  Standard size.
SET OF 12.

Fits:
Porsche 993 1994-98
Porsche 996 Turbo

Diagram Ref No 15.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99310314715

The product you are viewing cross references to these numbers