On Jan 8, 10:30*pm, "Maxwell" #$$9#@%%%.^^^ wrote:
wrote in message

...
On Jan 8, 3:56 pm, Monk wrote:

A Subaru?

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First off, we can forget about lost-foam or anything more exotic than
green-sand, simply because there aren't enough of us. *So we stick to
standard, readily available valves, valve guides, valve seats and
studs. *The fins make the castings pretty tricky but if it was easy
you would have seen it years ago.

So we make a L-head and an R-head; mirror images. *We do the best we
can with the fins but recognize our limitations and leave the most
difficult of them as CUT fins: Rather than try to cast perfect fins in
a couple of high-risk areas, we settle for a quarter-inch bar of
aluminum that's configured for easy SAWING, which we do as part of the
flash clean-up.

-R.S.Hoover

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I've alway thought it would be more practical to CNC saw all the cooling
fins. Seems a bit extreme at first glance, but if you go to the time or
expense to fabricate patterns to cast the heads, we must be talk about doing
more than just a couple of sets. So the programming cost might well be worth
the cooling efficency of extremely detailed cooling fins.

I disagree, sand casting would be easier than milling from solid
block. Just sculpt your head out of wax cover with sand and pour your
casting. A little grinding here and there and there you have it. OK,
not that simplistic, but you get the gist.