8mm Inlet Valve Guide - 2nd Oversize - Type 4 Engines - 12.21mm

This 2nd oversize inlet valve guide is intended for Type 4 air-cooled engines where the cylinder head valve guide bores have worn beyond first oversize or have been re-machined further during refurbishment. With an increased outer diameter of 12.21mm, this guide restores the correct interference fit in the head while retaining compatibility with standard 8mm inlet valve stems.

Valve guides are essential for maintaining precise valve alignment and stable valve movement. Excessively worn or loose guides can lead to poor valve sealing, increased oil consumption, blue exhaust smoke, and accelerated wear of both valves and seats. This second oversize (OS2) guide allows continued use of otherwise serviceable cylinder heads, making it ideal for professional engine rebuilds and high-quality restorations.

Manufactured to the correct 12.21mm OD x 8mm ID x 58mm length, this inlet valve guide suits 1700cc, 1800cc, and 2000cc Type 4 engines as fitted to VW T2 Baywindow buses, air-cooled VW T25 / T3 buses, and Porsche 914 models within the specified engine ranges.

Quantity and fitting notes:

• Sold individually

• 4 inlet valve guides required per complete engine

• Inlet valves only
  Because this is a second oversize guide, accurate machining of the cylinder head is critical. The head must be bored precisely to suit the 12.21mm guide before installation. After pressing in, the guide must be correctly sized (reamed or honed) to achieve proper valve stem clearance. Installation should be carried out by a competent engine machine shop.

Technical Specifications

• Part Type: Inlet valve guide (2nd oversize)

• Engine Type: VW Type 4 air-cooled

• Valve Stem Size: 8 mm

• Outer Diameter: 12.21 mm (OS2)

• Inner Diameter: 8 mm

• Length: 58 mm

• Application: Inlet valve

• Sold: Each

• Quantity Required: 4 per engine

Vehicle & Engine Compatibility

• VW T2 Baywindow: 1700cc, 1800cc, 2000cc air-cooled (1972–1979)

• VW T25 / T3 (air-cooled): 2000cc (1980–1983)

• Porsche 914:

  • 1700cc

  • 1800cc

  • 2000cc up to engine number GB0 010050