34mm X 9mm Valve - Type 4 Exhaust Valve - 1800cc (AW Engine Code)

This replacement exhaust valve is designed for Volkswagen Type 4 1800cc air-cooled engines, as fitted to Baywindow Buses from August 1973 to July 1974 and selected Porsche 914 models. It is a direct-fit reproduction valve manufactured to standard factory dimensions, making it ideal for routine engine rebuilds, top-end refreshes, or replacing worn or damaged original valves.

What this part does

The exhaust valve controls the release of burnt gases from the combustion chamber after ignition. Operating under extreme heat and pressure, the exhaust valve must seal perfectly against the valve seat to maintain compression, engine efficiency, and correct exhaust flow. A worn or pitted exhaust valve can cause compression loss, overheating, poor running, and eventual engine damage.

How it works

During the exhaust stroke, the camshaft opens the exhaust valve via the valve train, allowing spent gases to exit the cylinder and flow into the exhaust system. Once closed, the valve must seal completely to prevent hot gases from leaking back into the combustion chamber. This valve features a 34mm head for correct exhaust flow and a 9mm stem, as used on specific 1800cc Type 4 engines, ensuring compatibility with the original valve guides and cylinder heads.

Key specifications

• Valve head diameter: 34mm

• Stem diameter: 9mm

• Overall length: 117mm

• Grooves: 3

• Type: Exhaust valve

• Quality: Reproduction

• Quantity: Sold individually (4 required per engine)

Vehicle compatibility

• VW Baywindow Bus:

  • 1800cc Type 4 engines

  • Engine code AP

  • From 08/1973 to 07/1974

  • Up to engine number AP 027 465

• Porsche 914:

  • 1800cc Type 4 engines

  • Model years 1974–1976

Fitting notes

• Designed to work with standard valve guides and valve seats for 9mm stem exhaust valves

• Always check valve guides, seats, springs, and retainers during installation

• For best results, replace exhaust valves as a full set during an engine rebuild

• Valve lapping or professional seat cutting may be required depending on head condition

This exhaust valve is a reliable, cost-effective solution for maintaining correct engine operation and exhaust gas control in original-spec 1800cc Type 4 engines.