Engine cylinder head inlet valve. Porsche 955 Cayenne S / Turbo  ›  94810531102

The OE Match Engine Cylinder Head Inlet Valve is a precision replacement valvetrain component for Porsche Cayenne 955 4.5L V8 engines. It controls the flow of intake air and fuel into the combustion chamber and provides an essential seal against the valve seat when closed.

• Porsche 955 Cayenne S 4.5L 2003-06
• Porsche 955 Cayenne Turbo 4.5L 2003-06

During the intake stroke, the valve opens to allow the cylinder to fill with the intake charge. It then closes securely against the valve seat so the combustion chamber can build and retain the compression required for efficient combustion.

Correct inlet valve condition, alignment and seating are essential for effective cylinder filling, consistent compression, smooth engine operation and dependable performance.

What This Product Does:

• Controls the flow of intake air and fuel into the combustion chamber.
• Opens during the intake stroke to allow efficient cylinder filling.
• Closes against the valve seat to seal the combustion chamber.
• Helps maintain correct cylinder compression.
• Supports efficient combustion and engine performance.
• Helps maintain smooth idle and consistent power delivery.
• Contributes to responsive acceleration and throttle response.
• Works with the valve guide, valve seat, valve spring and associated valvetrain components.
• Replaces an inlet valve that has become bent, pitted, burnt or excessively worn.
• Helps restore correct cylinder-head operation during engine repair or rebuilding.

For correct operation, the valve must travel smoothly within its guide and make even contact with the valve seat. Wear, deposits or mechanical damage that prevent complete seating can allow compression to escape.

Symptoms Of Wear Or Failure:
Possible symptoms include:

• Reduced engine power.
• Rough or unstable idle.
• Engine misfires.
• Poor acceleration or throttle response.
• Low or uneven cylinder compression.
• Difficult starting.
• Increased fuel consumption.
• Uneven engine operation.
• Engine management warning light.
• Misfire-related fault codes.
• Ticking or abnormal valvetrain noise.
• Poor compression-test results.
• Leakage through the intake system during a cylinder leak-down test.
• Pitting or erosion of the valve face.
• Carbon build-up around the valve.
• Bent or damaged valve stem.
• Excessive valve-stem wear.
• Failure of the valve to seal correctly against its seat.

A leaking inlet valve can allow cylinder pressure to escape back into the intake tract instead of remaining within the combustion chamber, reducing compression and combustion efficiency.

Why Replacement Matters:
The inlet valve performs two important jobs: allowing the cylinder to fill efficiently and sealing the combustion chamber when closed.

During normal engine operation, the valve is subjected to continuous opening and closing cycles, high temperatures, combustion deposits and mechanical loads. Over time, the valve face, stem or seating surface can deteriorate.

A worn or damaged inlet valve may cause:

• Loss of cylinder compression.
• Reduced engine power.
• Rough running and misfires.
• Poor throttle response.
• Increased fuel consumption.
• Uneven performance between cylinders.
• Accelerated wear of the valve seat and guide.

Replacing a defective inlet valve helps restore correct intake flow, cylinder sealing and compression.