George Lendich wrote:

Paul /Butch,
Considering Butch's concerns about cutting into the face of the 
bellhousing causing stress risers and the fact that a area
is needed to be milled for the starter motor( to make it nice and 
flat). I think what is needed is a raised pad of 2mm across
both areas which would accommodate the milling process.

 Even if  most of the 2mm were milled -off, it would make for 
a better finish (more stress free). This would be off-set by
reducing the internal pad by the same amount and also the back 
of the bellhousing, where the depth is currently marginal.

I think what we would end-up with is a front pad of approx .5mm, 
reducing the depth of the internal housing .5mm, however
retaining the 90.9 mm overall depth.

Please consider these suggestions, when you get the housing.

There are also a number of other changes I'm considering
1. Reducing the front mounting pad thickness where it's not needed.
2. Reducing overall thickness of the walls to about 4.5mm.
3. Making the sides equal length.
4. Reducing the Draft of the walls to accommodate milling right 
angle to the face. There will be some extra thickness at the
wall at the time of pouring the housing but this would, for the most part, be milled-off.
5. Reducing the bulk of the internal mounting 'stand - offs'.
6. Reducing the excess depth of the strengthening ribs, 
(the excess have been milled-off on the prototype).

I'm hoping for a target weight of 12 lbs, or less if possible.

I still believe that an 'Investment Casting' would be the best 
alternative, it's a pity we don't have the numbers to make this
type of casting pay for itself. I believe we could get it to 9 lbs or less.
Getting there !!
George (down under)

 
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