8mm Inlet Valve Guide - 3rd Oversize - Type 4 Engines - 12.31mm

This 3rd oversize inlet valve guide is designed for Type 4 air-cooled engines where cylinder head valve guide bores have worn significantly or have been machined beyond second oversize during refurbishment. With an increased outer diameter of 12.31mm, this guide restores the correct interference fit in the cylinder head while continuing to use standard 8mm inlet valve stems.

Valve guides are fundamental to correct valve alignment, smooth valvetrain operation, and effective sealing between the valve and its seat. Severely worn or loose guides can cause high oil consumption, poor compression, valve chatter, and premature valve seat damage. This third oversize (OS3) guide allows heavily worn but otherwise serviceable Type 4 cylinder heads to be rebuilt correctly, extending their usable life and maintaining original engine specifications.

Manufactured to the correct 12.31mm OD x 8mm ID x 58mm length, this inlet valve guide is suitable for 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 listed engine ranges.

Quantity and fitting notes:

• Sold individually

• 4 inlet valve guides required per complete engine

• Inlet valves only
  Due to the size of this oversize guide, precise machining of the cylinder head is essential. The valve guide bore must be accurately machined to suit the 12.31mm outer diameter. After installation, the guide must be correctly sized (reamed or honed) to achieve the correct clearance for the 8mm valve stem. Professional installation by an experienced engine machine shop is strongly recommended.

Technical Specifications

• Part Type: Inlet valve guide (3rd oversize)

• Engine Type: VW Type 4 air-cooled

• Valve Stem Size: 8 mm

• Outer Diameter: 12.31 mm (OS3)

• 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