Very cool info on aluminum to magnesium case transition: part number cut off!
I emailed Bruce Anderson the other day with a question regarding how to identify if a '68 case was aluminum vs. magnesium. The case in question was out of state and the seller wasn't an expert, so he didn’t know how to tell. Bruce gave me the standard visual cues to relay to the seller, but apparently Bruce then got to working the phones. Here is what he sent me:
Quote:
Hi Kenik,
Got some more information.
The type numbers were the same for the 1968 engines with both the sand cast aluminum crankcase and the die cast magnesium crankcase. For the US cars the Type numbers were 901/14 for the manual transmission at 901/17 for the Sportomatic transmissions. These would be last numbers of the sand cast series: 901/14 3280631, 901/17 3380148
Beside the serial number the best way to tell is by looking at the crankcases. The sand cast aluminum crankcase has a rough sand cast finish and has sort of a bright silver look. The sand cast aluminum crankcases also had fins on the bottom of the crankcase, which the magnesium crankcase did not have. The die cast magnesium crankcase has a very smooth finish and a modeled gray color. The gray is the Dow Corning finish that Porsche used to slow down the corrosion process.
This is apparently new info and was not in his book. In follow up emails, he was just as surprised as I was that he was able to find this info, but he figured the challenge was worth it because in his words he felt "someone must know". I guess now we all do.
Thanks again to Bruce for this cool little tidbit.
