DenVogel

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.

theiceman

you want the lower turbo covers with the ribs if you are doing an upgrade and those are all aluminum.

oldskewel

In general, to tell magnesium vs. aluminum, you can put a small amount of acid (e.g., vinegar) on a cleaned surface and see what happens. There should be no reaction at all if it is aluminum. But with magnesium, you will see some bubbles almost immediately, and eventually some black.

theiceman

you may have just answered a question i have always wondered about .

My buddy rebuilds a lot of air cooled engines.. when some come back from the machine shop they are black ( case halves etc. ) Is this because they are magnesium and that is what the cleaning process does to them ? Do they remain black forever after that ??

DenVogel

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)

theiceman

looks like this guy sells them in aluminum if you are looking for exact replacements without reinforcement ribs on lowers.

https://www.carpoint.de/en/pair-valv...-lwb_1216_2147

Houpty GT

I believe the "aluminum" turbo valve covers are a ZA (zinc-aluminum) alloy. Neither mag nor aluminum wheel cleaners (hydrofluoric acid and ammonium bifluoride) removed any of their oxidation.