On Jan 17, 5:17*pm, Fred the Red Shirt
wrote:
On Jan 16, 6:08*pm, " wrote:







...

The objective is to produce TWO unique castings -- one forward, one
aft -- for the two barrels on each side of the VW engine.

...

Since these heads are not for vehicles, there is no limitation on the
height of the fins. *If the heads WERE for bugs or buses they would
have to fit UNDER the stock tin-ware, reducing the maximum fin height
to about one inch.

Based on the parting-line flash of new, stock heads, they are cast
using two molds. *To cast INDIVIDUAL heads it will take at least THREE
molds of FOUR different types. *Anyone having actual experience with
finned aluminum castings is encouraged to offer their opinion.
...

My experience is not with casting but with fin design. *Fins that
are longer than necessary will reduce the cooling.

Think of it this way: *As you move along from root to tip the
temperature in the fin drops. *If it drops to the same as
the air temperature before you reach the tip, all of the fin
between that point and the tip is wasted. *Actually worse
than wasted as cooling air passing over that outer part of
the fin doesn't cool *anything, as you're wasting air too.

That's an extreme situation, but the point is that there is an
optimum length for cooling fins given a fixed massflow of
cooling air.

And as mentioned before, tapering the fins in thickness from
root to tip helps to maximize the cooling and minimize the
weight too.

--

FF- Hide quoted text -

- Show quoted text -

Without a doubt the concept of a longer case and crank shaft for
increased bearing surface coupled with an improved head casting with
relocated exhaust valves and increased fin space is long past due. The
Corvair aircraft engine has now seen the introduction of a fifth
bearing surface as well as forged crankshafts becoming available, but
still in question as to long term reliability. Me, I’d be more than
willing to purchase improved VW “aircraft” engine parts for a build
project. Without a doubt others would to as such an engine would be
fantastic.

Joe S.