VW - Polished Crankcase II

Polished Crankcase

Don’t do it. Not if you intend to drive the vehicle. If it’s something for display, feel free to polish it to a nice shine. A coat of clear laquer will preserve the polish for about a year.

But if you intend to drive the vehicle, give the cleaned, deburred crankcase one final wash with hot soapy water followed by a boiling water rinse and allow it to air-dry. A touch of compressed air through the oil passages would be wise (and I assume all plugs are out).

Your clean, dry case should be protected with a thin coat of flat black paint on its exterior surfaces. Do not use a hi-temp paint as the high clay or eutectic metallic content that gives such paints their high-temperature qualities acts as a thermal insulator. What you want is a surface that will radiate heat. Polished surfaces reflect heat. If you polish your crankcase it will run considerably hotter than normal.

This isn’t an automotive hints & kinks sort of thing, it’s simple physics. Veedub drivers in cold climates have long known the benefit of chrome plated valve covers and push-rod tubes. The heat-reflective surfaces cause the engine to run from ten to thirty degrees hotter.

The original Volkswagen engines (1935-37) was designed for a service life of 100,000 km; it didn’t even have replaceable bearing shells. But through the use of full-flow oil filtration systems the service life of a properly assembled VW engine can exceed 300,000 km, which means the engine may be exposed to the elements for 20 years or more, and that justifies a protective coat of paint.

Flat black paint is virtually transparent to heat radiation. Giving your crankcase, push-rod tubes and valve covers a coat of flat black paint atop bare metal actually promotes engine cooling. One of the quickest ways to spot a professionally built engine is from its somber flat-and matte-black surfaces.