Chain guide rail. Porsche 996 / 997

Chain guide rail.
This guide rail ensures the timing chain follows the correct path, maintaining chain alignment and tension over the life of the engine. The guide is engineered to resist wear from chain contact, vibration, thermal expansion and age. It installs into the existing timing cover without modification. It is used on the left/right-hand / lower side (depending on engine layout) and works in conjunction with the chain tensioners and other guide rails to keep valve timing accurate and engine operation smooth.

Fits:
Porsche 996 Turbo 2001 - 2005
Porsche 996 GT3 2000 - 2005
Porsche 997 Turbo 2007 - 2011
Porsche 997 GT3 2007 - 2011

Diagram ref no 21

Ideal for engine rebuilds, timing-chain replacements, or preventive maintenance on high-mileage engines.

This chain guide rail:
• Guides the timing chain to follow the correct path between crankshaft, camshafts, and intermediate shafts - ensuring synchronised valve timing.
• Maintains chain tension and alignment under load and throughout thermal cycles, preventing chain slippage or jumping that could damage the engine.
• Reduces noise, rattles, and wear that occur when the chain rubs against incorrect or worn surfaces.
• Serves as a critical component for overall engine longevity and reliability, especially in high-mileage or performance-oriented engines.

Timing-chain guide rails wear over time due to constant metal-to-plastic/rubber contact, heat, and vibration. A worn guide rail can lead to:
• Chain misalignment, slippage or jumping - risking engine timing errors, valve-to-piston contact, or catastrophic engine damage
• Excessive timing noise, rattling, or vibration
• Premature wear on chain, sprockets, and tensioners - leading to costly repairs.

Replacing with a correctly spec’d guide rail restores proper chain pathing, prolongs timing-system life, and helps avoid severe engine damage.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99610516

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