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Valve control adjustment hexagon nut M8x1 Porsche 911 / 964 / 914 - 99903400500
99903400500/1
Vehicle Group
- Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
- Porsche 911 1978-1983 3.0L / SC
- Porsche 911 1984-1986 3.2L
- Porsche 911 1987-1989 3.2L G50
- Porsche 911 1975-1977 3.0L Turbo (930)
- 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 914 (1970-1976)
Information
Hexagon nut M8x1 for valve control adjustment screw, left.
This locking nut is critical in maintaining the correct clearance setting between the rocker-arm or cam follower and valve stem, ensuring reliable valvetrain performance and correct engine behaviour.
Sold each.
Fits:
Porsche 911 1973 - 1989
Porsche 911 Turbo 1975 - 1989
Porsche 964 C2 / C4 / RS 1989 - 1994
Porsche 964 Turbo 1991 - 1994
Porsche 914 1970 - 1976
Porsche 914/6 1970 - 1972
Diagram ref no 50
• Position on Vehicle: Engine cylinder head, at the valve adjusting screw area - used to lock the adjuster once clearance is set.
• Function: Locks the valve-adjusting screw in place, ensures the correct clearance remains unchanged under engine operation, prevents loosening of adjuster and ensures valvetrain reliability.
• Specification: M8 × 1 thread, correct height and socket size, treated or coated for durability - direct-fit replacement of Porsche part number 99903400500.
• Applications: Ideal when your original nut is damaged, the adjuster is loose, you are doing a valve-clearance service, or you require reliable hardware for engine rebuilds.
While small, this locking nut performs a vital role: without it, the adjuster can drift, valve clearance can open up or close down, leading to noisy operation, performance loss, premature wear or even engine damage. Symptoms of a failing/incorrect nut include adjusting screw backing out, noisy valvetrain, incorrect clearance and poor idle or performance.
When to replace:
• The adjuster locking nut is missing, corroded, rounded or damaged.
• After valve-clearance adjustment and you want guaranteed lock-in of the setting.
• During engine rebuild or cylinder-head service when valvetrain hardware is exposed.
• To replace the original with fresh hardware to maintain service integrity and reliability.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99903400500
The product you are viewing cross references to these numbers
This locking nut is critical in maintaining the correct clearance setting between the rocker-arm or cam follower and valve stem, ensuring reliable valvetrain performance and correct engine behaviour.
Sold each.
Fits:
Porsche 911 1973 - 1989
Porsche 911 Turbo 1975 - 1989
Porsche 964 C2 / C4 / RS 1989 - 1994
Porsche 964 Turbo 1991 - 1994
Porsche 914 1970 - 1976
Porsche 914/6 1970 - 1972
Diagram ref no 50
• Position on Vehicle: Engine cylinder head, at the valve adjusting screw area - used to lock the adjuster once clearance is set.
• Function: Locks the valve-adjusting screw in place, ensures the correct clearance remains unchanged under engine operation, prevents loosening of adjuster and ensures valvetrain reliability.
• Specification: M8 × 1 thread, correct height and socket size, treated or coated for durability - direct-fit replacement of Porsche part number 99903400500.
• Applications: Ideal when your original nut is damaged, the adjuster is loose, you are doing a valve-clearance service, or you require reliable hardware for engine rebuilds.
While small, this locking nut performs a vital role: without it, the adjuster can drift, valve clearance can open up or close down, leading to noisy operation, performance loss, premature wear or even engine damage. Symptoms of a failing/incorrect nut include adjusting screw backing out, noisy valvetrain, incorrect clearance and poor idle or performance.
When to replace:
• The adjuster locking nut is missing, corroded, rounded or damaged.
• After valve-clearance adjustment and you want guaranteed lock-in of the setting.
• During engine rebuild or cylinder-head service when valvetrain hardware is exposed.
• To replace the original with fresh hardware to maintain service integrity and reliability.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99903400500
99903400500
The product you are viewing cross references to these numbers
Price: £1.25
In stock
Related products
Vehicle Group
- 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
Information
Rocker arm INLET.
6 per engine. Sold each.
Fits:
Porsche 993 1994-98
Diagram ref no 22.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99310508500
The product you are viewing cross references to these numbers
6 per engine. Sold each.
Fits:
Porsche 993 1994-98
Diagram ref no 22.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99310508500
313096880322
313 09 688 03 22
99310508500
99310508526
The product you are viewing cross references to these numbers
Price: £69.00
In stock
Vehicle Group
- 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
Information
Rocker arm OUTLET
6 per engine. Sold each.
Fits:
Porsche 993 1994-98
Diagram ref no 23.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99310508600
The product you are viewing cross references to these numbers
6 per engine. Sold each.
Fits:
Porsche 993 1994-98
Diagram ref no 23.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99310508600
313096890322
313 09 689 03 22
99310508600
99310508201
The product you are viewing cross references to these numbers
Price: £69.00
In stock
Vehicle Group
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
Information
Hydraulic valve tappet. Price is each
Fits:
Porsche 993 Turbo M64.60
Click 'Zoom in' for large parts diagram.
Diagram ref no 25
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99310514103
The product you are viewing cross references to these numbers
Fits:
Porsche 993 Turbo M64.60
Click 'Zoom in' for large parts diagram.
Diagram ref no 25
Related reference numbers
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99310514103
18708
99310514105
420005110
The product you are viewing cross references to these numbers
Price: £62.00
In stock
Vehicle Group
- Porsche 911 1965-1968 2.0L / 912 SWB (F)
- Porsche 911 1968-1973 2.2L / 2.4L / 2.7L RS LWB (F)
- Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
- Porsche 911 1978-1983 3.0L / SC
- Porsche 911 1984-1986 3.2L
- Porsche 911 1987-1989 3.2L G50
- Porsche 911 1975-1977 3.0L Turbo (930)
- 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) 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
Information
Rocker arm bush. Semi finished. Requires machining.
Width: 26mm
Shaft dia: 18mm
Housing dia: 20mm
Bronze coated steel back
Fits:
Porsche 911 1965-89
Porsche 964 1989-94
Porsche 993 1994-97
Click 'Zoom in' for large parts diagram.
Diagram ref no 31
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
90110534101
The product you are viewing cross references to these numbers
Width: 26mm
Shaft dia: 18mm
Housing dia: 20mm
Bronze coated steel back
Fits:
Porsche 911 1965-89
Porsche 964 1989-94
Porsche 993 1994-97
Click 'Zoom in' for large parts diagram.
Diagram ref no 31
Related reference numbers
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90110534101
9400048
93010504302
93010504305
93010504300
930105043EX
99310508500
99310508600
The product you are viewing cross references to these numbers
Price: £5.95
In stock