Engine Valves / Guides / Springs

The OE Match Engine Cylinder Head Inlet Valve is a precision replacement valvetrain component designed for selected Porsche 996 Turbo, 996 GT2, 997 Turbo, 997 GT2 and GT2 RS 3.6L engines.

• Porsche 996 Turbo/GT2 2001-05
• Porsche 997.1 Turbo / GT2 3.6L 2007-09
• Porsche 997.2 GT2 RS 3.6L 2011

The inlet valve controls the flow of the intake charge into the combustion chamber. During the intake stroke, it opens to allow the cylinder to fill before closing securely against the valve seat for the compression and combustion phases.

Correct valve condition, alignment and seating are essential for maintaining cylinder compression, efficient airflow and consistent engine performance. This is particularly important in high-performance turbocharged engines, where reliable cylinder sealing and airflow are critical under increased boost pressure and engine load.

What This Product Does:

• Controls the intake of air 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 breathing.
• Helps maintain throttle response and engine performance.
• Works with the valve guide, valve seat, valve spring and associated valvetrain components.
• Helps maintain reliable operation in high-performance turbocharged engines.
• 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 move smoothly within its guide and form an even seal against the valve seat. Wear or damage that prevents complete seating can allow compression to escape and reduce engine efficiency.

Symptoms Of Wear Or Failure:
Possible symptoms include:

• Low or uneven cylinder compression.
• Engine misfires.
• Rough or unstable idle.
• Reduced engine power.
• Poor acceleration or throttle response.
• Difficulty starting.
• Increased fuel consumption.
• Uneven engine running.
• Check engine or engine-management warning light.
• Misfire-related fault codes.
• Ticking or abnormal valvetrain noise.
• Poor compression-test results.
• Leakage through the intake tract during a cylinder leak-down test.
• Pitting or erosion of the valve face.
• Carbon deposits 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 system rather than remaining within the combustion chamber.

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

During engine operation, the valve is exposed to continuous opening and closing cycles, high temperatures, combustion deposits and significant mechanical loading. In turbocharged engines, reliable valve sealing becomes particularly important because the engine operates under substantial cylinder pressures.

Over time, an inlet valve may suffer from:

• Valve-face pitting or erosion.
• Carbon build-up.
• Valve-stem wear.
• Mechanical distortion.
• Damage caused by poor seating.
• Wear associated with excessive valve-guide clearance.
• Damage caused by valve-to-piston contact.

A worn or damaged valve can lead to compression loss, misfires and reduced engine output.

Replacing a defective inlet valve helps restore:

• Correct cylinder sealing.
• Strong compression.
• Efficient intake airflow.
• Smooth engine operation.
• Consistent power delivery.
• Reliable turbocharged engine performance.
• Correct valvetrain operation.

Fits:
Porsche 986 Boxster 1997-04
Porsche 987 Boxster 2005-08
Porsche 987C Cayman 2007-08
Porsche 996 C2/ C4 / C4S 1998-05
Porsche 997 C2 / C2S / C4 / C4S 2005-08

Price is for each.

Click picture for large parts diagram.
Diagram Ref No 14.

Exhaust valve guide 41.91mm by OE Match for selected Porsche 996 and 997 GT3 and Turbo engines, supplied as an OE-style replacement for correct valve location in the cylinder head.

What This Product Does
This exhaust valve guide supports and locates the exhaust valve stem in the cylinder head, helping to maintain alignment, minimise side loading, and provide a controlled path for heat transfer away from the valve.

Functions

• Guides the exhaust valve stem within the cylinder head
• Helps maintain valve seating accuracy for consistent sealing
• Provides a running surface for the valve stem to reduce wear
• Contributes to heat transfer from the valve into the cylinder head

Symptoms of Fault

• Blue smoke on overrun or deceleration
• Increased engine oil consumption
• Rough idle or misfires linked to poor valve sealing
• Low compression or high leak-down readings via the exhaust side
• Ticking or tapping noises from the valvetrain area

Why Replacement Matters
Worn or damaged valve guides can affect valve seating, increase oil consumption and contribute to combustion deposits. During top-end or full engine rebuilds, guides are typically renewed along with valves, stem seals and related hardware while the cylinder heads are dismantled, reducing the likelihood of repeat strip-downs after reassembly.

Fits

• Porsche 996 (911) (1997–2005)
• Porsche 996 (911) (1997–2005) ⇒ 996 TURBO 2000–05
• Porsche 996 (911) (1997–2005) ⇒ 996 GT3 MKI 1999–02
• Porsche 996 (911) (1997–2005) ⇒ 996 GT3 MKII 2003–>>
• Porsche 996 (911) (1997–2005) ⇒ 996 GT3 RS 2003–04
• Porsche 997 (911) MK1 2005–2008
• Porsche 997 (911) MK1 2005–2008 ⇒ 997 MK1 TURBO 2007–09
• Porsche 997 (911) MK1 2005–2008 ⇒ 997 MK1 GT3 / GT3 RS 2007–09
• Porsche 997 (911) MK2 2009–2012
• Porsche 997 (911) MK2 2009–2012 ⇒ 997 MKII GT3 / GT3 RS 2010–11
• Porsche 997 (911) MK2 2009–2012 ⇒ 997 MKII Turbo 2010–13

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

Key Dimensions & Material
Material: copper
Inner diameter: 5.92mm
Outer diameter: 10.54mm
Length: 41.91mm

The Genuine Porsche Inlet Valve, 41mm (Part Number: 99710511190) is an original equipment engine cylinder head component designed for selected Porsche 911 GT3 and GT3 RS models, including the 997-generation 3.6L, 3.8L and 4.0L naturally aspirated flat-six engines.
Sold Each.
x12 Required Per Car.

Fits:

• Porsche 997 MK1 GT3 / GT3 RS 2007-09
• Porsche 997 MKII GT3 / GT3 RS 2010-11  

Featuring a 41mm valve head diameter, the component is designed for Porsche's high-performance GT engines, where accurate valve operation is essential for maintaining efficient cylinder filling, combustion performance and reliable high-RPM operation.

During engine operation, the inlet valve opens to allow fresh air to enter the combustion chamber and closes to create the necessary seal during compression and combustion. Its movement is controlled by the camshaft and associated valvetrain components.

The Porsche GT3 and GT3 RS engines operate at exceptionally high engine speeds, placing significant demands on their valves, valve springs, guides and sealing surfaces. The inlet valve must withstand repeated mechanical loading, rapid opening and closing cycles and elevated operating temperatures.

Over time, an inlet valve may become worn, bent, damaged or unable to seal correctly because of valve seat deterioration, carbon deposits, overheating or mechanical problems within the valvetrain.

A damaged inlet valve can reduce cylinder compression, disturb combustion and cause rough running, misfires or loss of engine performance.

Replacing a defective inlet valve with a Genuine Porsche component helps restore correct valve operation, maintain cylinder sealing and protect the engine from further mechanical damage.

Ideal for cylinder head repairs, engine rebuilding, valve replacement and specialist Porsche GT engine maintenance, this Genuine Porsche 41mm Inlet Valve provides a factory-specified replacement for compatible applications.

What This Product Does:
The inlet valve is a critical component of the engine's four-stroke combustion cycle.

Its primary function is to control the flow of fresh intake air into the combustion chamber while maintaining a secure seal when the valve is closed.

As the piston moves through the intake stroke, the inlet valve opens at the correct point in the engine cycle to allow air to enter the cylinder.

The valve then closes as required by the camshaft timing, enabling the cylinder to develop compression before combustion.

The 41mm valve head is designed to provide the intended airflow and sealing characteristics for the relevant Porsche GT engine cylinder head.

Its main functions include:

• Controlling intake airflow: Opens to allow fresh air to enter the combustion chamber.
• Maintaining cylinder compression: Closes against the valve seat to provide the seal required for compression and combustion.
• Supporting efficient cylinder filling: Helps the engine receive the correct volume of intake air according to its design and operating conditions.
• Maintaining combustion efficiency: Supports the controlled intake and compression processes required for normal combustion.
• Supporting engine performance: Contributes to the airflow characteristics required by Porsche's naturally aspirated high-performance engines.
• Enabling high-RPM operation: Operates as part of a precision valvetrain designed for demanding engine speeds.
• Working with the camshaft: Opens and closes according to the engine's specified valve timing.
• Supporting smooth engine operation: Correct valve seating helps maintain consistent compression and combustion between cylinders.
• Preserving original engine specifications: Maintains the intended inlet valve dimensions and configuration.

The inlet valve is a mechanical engine component. It does not independently control fuel injection, ignition timing or electronic engine management.

Symptoms Of Wear Or Failure:
Inlet valves are subjected to repeated opening and closing cycles, elevated temperatures, valve spring pressure and mechanical contact with their seats and guides.

Although designed for demanding engine operation, damage or deterioration can occur through excessive wear, overheating, poor lubrication of related valvetrain components or mechanical interference.

Common symptoms of a worn or damaged inlet valve include:

• Loss of engine compression: A burnt, bent or poorly seated inlet valve may prevent the cylinder from sealing correctly.
• Engine misfires: Reduced compression or poor valve sealing can cause inconsistent combustion in the affected cylinder.
• Rough engine idling: Uneven cylinder performance may result in unstable or irregular idle operation.
• Reduced engine power: Poor cylinder filling or compression loss may affect engine performance.
• Hesitation during acceleration: A cylinder affected by valve damage may not produce its expected power output.
• Difficulty starting: Significant compression loss may make the engine harder to start.
• Abnormal valvetrain noises: Damage to associated valve springs, guides or operating components may produce unusual mechanical noise.
• Excessive valve guide wear: A worn guide may allow excessive valve movement and compromise correct seating.
• Bent valve stem: Mechanical interference or incorrect valve timing can deform the valve and prevent proper closure.
• Damaged valve head or seating surface: Pitting, burning or impact damage may reduce sealing effectiveness.
• Increased oil consumption: Worn valve guides or stem seals may allow oil to enter the intake port and combustion chamber.
• Blue exhaust smoke: Oil entering the combustion chamber through damaged valve guide or seal arrangements may produce blue smoke.
• Check engine warning: Cylinder misfires caused by compression problems may trigger engine management fault codes.
• Poor cylinder leak-down test results: Air escaping through the intake port during testing may indicate an inlet valve sealing problem.
• Visible damage during cylinder head inspection: Cracks, deformation, excessive stem wear or damaged seating surfaces may indicate replacement is necessary.

A valve that does not seal correctly may allow compressed air to escape from the combustion chamber, reducing the efficiency of the combustion process.

A bent, cracked or otherwise weakened inlet valve can also represent a serious mechanical risk, particularly when the engine is operated at high RPM.

If a valve fails completely, fragments may damage the piston, cylinder head or other internal engine components.

Installing a Genuine Porsche replacement Inlet Valve helps to:

• Restore cylinder compression: Replace damaged sealing surfaces and restore the intended valve-to-seat contact.
• Improve combustion consistency: Help eliminate irregular combustion caused by a confirmed valve sealing fault.
• Restore engine performance: Support correct intake airflow and cylinder operation.
• Reduce engine misfires: Address misfires caused by a leaking or damaged inlet valve.
• Maintain high-RPM reliability: Replace mechanically compromised components before further deterioration.
• Protect internal engine components: Reduce the risk of damage associated with a weakened or fractured valve.
• Restore correct valvetrain operation: Maintain the intended interaction between the valve, guide, spring and camshaft-driven components.
• Support cylinder head repairs: Provide the correct replacement part during specialist head refurbishment.
• Maintain original airflow characteristics: Preserve the specified 41mm inlet valve dimensions.
• Preserve factory engine specifications: Use a valve designed for the relevant Porsche GT engine.
• Support engine rebuilding: Replace damaged or worn valves during an engine overhaul.
• Improve long-term engine reliability: Address mechanical wear before it causes additional cylinder head or piston damage.
• Maintain Genuine Porsche quality: Use an original equipment component intended for the applicable engine configuration.

Replacement is particularly recommended when inspection confirms valve deformation, cracking, excessive stem wear, damaged seating surfaces or an inability to maintain proper cylinder compression.

When replacing an inlet valve, the valve guide, seat, spring, stem seal, retainers and associated valvetrain components should also be inspected.