"To plenum or not to plenum, that seems to be the question lately."

I am certainly no expert on cooling air-cooled engines, as I am going to use
a liquid cooled one.  However those of you who are interested might want to
look at an article in the August 2003 "Sport Aviation" on air cooling.  It
had an Excel spreadsheet which enables you to calculate the optimum
dimensions etc, and calculates the resulting drag.  The spreadsheet is still
available on the EAA website and can be downloaded.

EAA did the same thing in January 2004 for liquid cooled engines, and again
that spreadshet is available on their website.  I have not looked into the
air cooled spreadsheet, but the liquid cooled one is invaluable.

Jerry Fisher