We were discussing aluminum side and intermediate housings a couple of
weeks ago.  A figure of somewhere around 15lbs per housing in weight
savings was thrown out.  The exact figure isn't as important the fact
that several Delta builders have had to stack approximately that much
weight in the tail to get the proper W&B.  At $1400, one aluminum
housing could possibly save me 30lbs, which is just under $50/lb.
$50/lb is the figure that I like to use when deciding if more money is
worth the weight savings.

So, from the aluminum housings look like a winner, except that I read
one of Mazda's brochures for the RX-8.  In the engine section they go on
about how the engineers have worked so hard to reduce the engine weight,
and how engineers of performance autos will give up major limbs to drop
a few pounds.

So why did they continue with the cast iron housings?  They had to
redesign the castings for different exhaust anyway, and I assume the
engineers have internet access and can look at what the racing shops are
selling.  It seems that having to deal with only one type of casting
material would simplify things.  Would the wear surface treatments still
be prohibitively expensive even in production runs, or is there some
hidden reliability gotcha that isn't advertised well?