On Jan 12, 8:13*pm, "
wrote:

Examples of lost foam casting of the complexity required are quite
common.
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Alas, I haven't found any.

The stuff is a casting and the fin length is approaching 4 inches.
Volkswagen apparently uses metal molds and sand cores, this based on
working with a few VW heads.

Trying to TIG additional fins onto the existing finds proved
impractical for two reasons, the material used, and the expertise of
the welding. (I'm not that good a weldor -- I had to keep the things
in a box and use a bare electrode to get at the joint, even after
cutting away the existing fins on an angle so as to give me more room.
Once the chamber was heated to approximately 450*F, the welded portion
of the fin started to move around, typically 'leaning' over to touch
the adjacent fin, which shut off -- or upset -- the air-flow. I tried
1/8" 3003, some 5052 (I think .120) cast tooling plate (1/8) and fins,
salvaged from other heads. The latter gave the best results... but
only on the short sections, where I was TIGging to a fairly heavy
section (ie, adjacent to the exhaust stack or to the portion of the
head bearing the valve guide) But that didn't give enough fin area to
make much of a change in the temperature of the cooling-air. (I
measured it going in & coming out.)
After a LOT of effort I got two heads. Two STOCK heads. Which didn't
fit my jigs :-) ...one of those little details I sorta overlooked.
It was a bit discouraging.
Reading about Kyoto Ceramics and their efforts to produce a precision-
ground crystal for use in a wrist-watch, I figure I just didn't try
hard enough. Perhaps the isolated heads hold the answer, although I
recall the amount of effort put into their development by the
helicopter guy -- who was no dummy. (George(?) somebody? He knew his
engines and it looked like a shop to work in... except for its
location :-)

-Bob