The other thing the racers have discovered is that the shape of the duct
immediately behind the intake is critical. The NC lathe machined airfoil

section

aluminum intake tube shown here was a very noticeably improvement in the
amount of air actually ingested into the intake. This manifested
itself in a large drop in cylinder head temps allowing the diameter
of the holes to be reduced for the same cooling.

Therefore I suggest a larger single hole version of this be used near the
bottom front of the cowling (chin intake) to cool the rotary. I suggest
a round hole about six inches in diameter would be about right.
It would have the benefit of being in an area of high prop slipstream
velocity for good cooling on the ground and during climb and should
have a minimal effect on drag.

Paul Lamar

George Lendich wrote:

Paul,
What is that raised section, behind the opening. It seems like some sort of
restrictor.
George (dowm under)

Both cooling ducts curve upward towards the top of the cylinders.
In the carb air inlet there is a K&N filter. On the front of that there is 
a model airplane engine spinner to streamline the K&N filter. Worth
a 1/2 in intake manifold pressure.

Paul Lamar
 
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