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- 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)

Fits:
Porsche 356 B (1960 - 1963)
Porsche 356 C (1963 - 1965)
Porsche 911 F (1965 - 1969)
Click 'Zoom in' for large parts diagram.
Diagram ref no 19
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
61610531200
The product you are viewing cross references to these numbers
- Porsche 911 1965-1968 2.0L / 912 SWB (F)
- Porsche 356B 1959-63
- Porsche 356C 1963-65
The locking nut is designed for securing the valve-adjusting screw in classic Porsche 911, 914 and 964 series. It locks the valve-adjuster screw after proper clearance has been set.
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
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99903400500
The product you are viewing cross references to these numbers
- 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)
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
- 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)
Rocker Arms (Cam Followers) & Tappets – Precision Valve Train Components for Porsche Engines
The rocker arms (also known as cam followers) and tappets are crucial components within your Porsche’s valvetrain system. They convert the rotational movement of the camshaft into the vertical motion that opens and closes the engine’s valves, allowing precise control of air, fuel, and exhaust flow.
At Design911, we offer a complete range of rocker arms and tappets developed for Porsche engines across all generations. Manufactured from high-strength, wear-resistant alloys, these components ensure smooth operation, minimal friction, and long-lasting durability. Whether you’re restoring a classic air-cooled 911 or upgrading a modern GT engine, our quality valvetrain components deliver the accuracy and reliability your Porsche demands.
What Do Rocker Arms & Tappets Do?
Rocker arms and tappets form the mechanical link between the camshaft and the valves — controlling the timing and lift that determine engine breathing efficiency.
Core Functions:
- Transmit
camshaft movement to open and close the intake and exhaust valves.
- Maintain
precise valve timing for efficient combustion.
- Reduce
friction and wear through precise geometry and lubrication.
- Ensure
smooth, quiet operation across the rev range.
- Support consistent power delivery and optimal performance.
Well-functioning rocker arms and tappets are essential for maintaining engine efficiency, throttle response, and durability.
Why Do Rocker Arms & Tappets Fail?
Continuous exposure to high temperatures, pressure, and friction makes rocker arms and tappets susceptible to wear over time.
Common Causes of Failure Include:
- Oil
starvation due to blocked passages or poor lubrication.
- Surface
wear or pitting from high mileage or contamination.
- Excessive
valve clearance leading to noise and impact damage.
- Camshaft
wear causing uneven contact and mechanical stress.
- Material fatigue from prolonged high RPM use.
Symptoms of failure include ticking or knocking noises, loss of power, misfires, or excessive valve noise, all indicating the need for inspection and replacement.
Why Replace Valvetrain Components?
Replacing worn rocker arms or tappets restores accurate valve timing, reduces friction, and prevents camshaft or valve damage. Our high-performance, precision-engineered replacements are designed for exact fitment and long-term durability under extreme conditions.
Key Benefits:
- Restores proper valve timing and smooth operation.
- Reduces engine noise and friction losses.
- Prevents premature wear of the camshaft and valves.
- Manufactured from heat-treated, wear-resistant materials.
- Direct-fit
compatibility for a wide range of Porsche engines.
- Ideal for rebuilds, restorations, or performance upgrades.
A reliable valvetrain system ensures your Porsche runs smoother, quieter, and more efficiently — preserving both performance and longevity.
Highlights:
- High-strength rocker arms, cam followers, and tappets for Porsche engines.
- Precision-machined for durability and accurate valve control.
- Reduces noise, friction, and wear under extreme conditions.
- Perfect for rebuilds, tuning, and classic restoration projects.
- Direct-fit, manufacturer-quality parts for 911, Cayman, Boxster and other models.
- Essential for smooth, consistent engine performance.