Michael,
The Porsche 911 air cooled engine was a dry sump engine; the whole case was
made of magnesium. In all my experience with Porsche, over many years, I
have never, ever heard of an engine case 3rotting2 or breaking randomly.
Certainly, though, magnesium has a much greater tendency to fracture before
some other metals and alloys, but it would take some doing to get that to
happen even to a 40 year old magnesium engine case. Having said that, I
know the Porsche magnesium engine cases can definitely corrode and become
pitted badly, but only when completely neglected with water sitting on or in
them for a very long time. The reason Porsche eventually moved to aluminum
engine cases was only because the magnesium cases, which started out with a
2 liter displacement tended to warp increasingly more (and leak oil) as the
engine displacements grew from 2.2, 2.4 to 2.7 liters, increasing the
engines9 heat generation with each step up. I would never have guessed it,
but aluminum cases are stiffer than the magnesium cases.
Anyway -- back to wheels -- could it be that real magnesium wheels were a
bit porous to begin with, even when new, which is part of the reason why the
old mag wheels needed tubes in the day (beyond the bead design)?
On 5/19/10 7:52 PM, "michael king" <michael.s.king@gmail.com> wrote:
>
>
> On 20 May 2010 08:24, Would U.Believe <mcdangerous@verizon.net> wrote:
>> There are going to be a whole lot of Porsche 911 engines disintegrating if
>> that's the case. They were magnesium until the 3.0 liter engine came out
in
>> somewhere around 1980. This is the first I've heard about magnesium
>> "rotting".
>
> Mauro
>
> Magnesium wheels are well known for turning porus "rotting" they become
very
> brittle and fracture. As for other magnesium parts.. its not an uncomon
issue
> on magnesium sumps.
>
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