Engine cylinder head exhaust valve. Porsche 911 (993) 3.8 Carrera RS  ›  99310541943

The OE Match Engine Cylinder Head Exhaust Valve is a precision replacement valvetrain component for the Porsche 911 (993) 3.8 Carrera RS. It controls the release of burnt combustion gases from the cylinder and provides an essential seal against the valve seat when closed.

• Porsche 911 (993) 3.8 Carrera RS 1995-96 (M64.20)

During the exhaust stroke, the valve opens to allow combustion gases to leave the cylinder and flow into the exhaust system. It then closes firmly against the valve seat, helping the combustion chamber retain the compression required during the following engine cycle.

Because exhaust valves are directly exposed to extremely hot combustion gases, they operate under demanding thermal and mechanical conditions. Correct valve condition, alignment and seating are therefore essential for maintaining compression, efficient combustion and reliable engine performance.

What This Product Does:

• Controls the release of exhaust gases from the combustion chamber.
• Opens during the exhaust stroke to allow burnt gases to leave the cylinder.
• Closes against the valve seat to maintain combustion-chamber sealing.
• Helps maintain correct cylinder compression.
• Supports efficient combustion and engine performance.
• Helps maintain consistent power delivery and smooth engine operation.
• Works with the valve guide, valve seat, valve spring and associated valvetrain components.
• Replaces an exhaust valve that has become burnt, bent, pitted or excessively worn.
• Helps restore correct cylinder-head operation during an engine rebuild.

For correct operation, the valve must move smoothly within its guide and contact the valve seat evenly around its circumference. Wear or damage that prevents complete seating can allow compression and hot combustion gases to escape.

Symptoms Of Wear Or Failure:
Possible symptoms include:

• Low or uneven cylinder compression.
• Engine misfires.
• Rough or unstable idle.
• Loss of engine power.
• Poor acceleration or throttle response.
• Difficult starting.
• Increased fuel consumption.
• Irregular exhaust note.
• Ticking or abnormal valvetrain noise.
• Poor compression-test results.
• Leakage through the exhaust during a cylinder leak-down test.
• Pitting or erosion of the valve face.
• Burnt or damaged valve seating surface.
• Bent or damaged valve stem.
• Excessive valve-stem wear.
• Heavy carbon deposits.
• Failure of the valve to seal correctly against its seat.

A leaking exhaust valve allows combustion pressure to escape into the exhaust port rather than remaining within the cylinder, reducing compression and engine efficiency.

Why Replacement Matters:
The exhaust valve operates in one of the most thermally demanding areas of the engine. Every combustion cycle exposes the valve head and seating surface to extremely hot exhaust gases while the valve repeatedly opens and closes at high speed.

Over time, the valve can suffer from:

• Valve-face erosion.
• Burning or pitting.
• Carbon build-up.
• Valve-stem wear.
• Mechanical distortion.
• Overheating.
• Damage caused by incorrect valve seating.
• Wear associated with excessive valve-guide clearance.

Once the valve can no longer seal correctly, cylinder compression may fall and engine performance can deteriorate.

Replacing a defective exhaust valve helps restore:

• Correct combustion-chamber sealing.
• Cylinder compression.
• Smooth engine operation.
• Consistent power delivery.
• Efficient exhaust-gas control.
• Correct valvetrain operation.
• Long-term cylinder-head reliability.