ID Aluminum Valve Covers

[dennisv]

Is there an easy way to distinguish magnesium valve covers from aluminum? I had assumed that you could use the part number. Unfortunately if I compare the valve cover part numbers from the Porsche PDF parts catalogs 1970-76 (914-6 / 911T) magnesium to 1978-83 (911) aluminum, they are the same:

• Upper: 901 105 115 03
• Lower: 930 105 116 00 or 930 105 116 05

I am considering picking up some used aluminum valve covers from eBay or one of the classifieds sections as an upgrade to our 914-6 engine.

Thanks.

[stownsen914]

Mag usually oxidizes to a darker gray color compared to aluminum

[ChrisHamilton]

If you pour some household vinegar on the cover it will react if it's magnesium. It will bubble and fizz (the vinegar). If aluminum there will be no reaction. Do it in a inconspicuous place as the vinegar will etch it to an extent. Underside would be best. Rinse it with water when finished with the test.

[safe]

Correct me, but uppers are magnesium until the 964 (maybe those too, mine were horribly corroded) and lowers magnesium except for the 930 ones.
You really feel the weight difference, magnesium are way lighter than aluminum, 33% lighter than aluminium.

[dennisv]

Would perhaps the casting numbers found on the inside surface have changed from magnesium to aluminum? Here is what I found on our 914-6 engine, presumably original magnesium:

• 901.105.115.0R - Top x 2
• 901.105.116.0R - Bottom x 2
• 901.105.105.2R - Back left (911 orientation)
• 901.105.106.1R - Back right (911 orientation)

[strictly]

I think the upper magnesium covers were also typically painted black

[dennisv]

Originally Posted by strictly

I think the upper magnesium covers were also typically painted black

The ones we took off our 914-6 (911T) were black, but we had no way to know if they were original. Perhaps that explains it.