Re: rear vents on original GT\'s
Interesting... I'm in the middle of aerodynamic design of my scratch built car's bodywork. With the slope on the rear vertical valance (where the exhausts poke through) of the GT40, it's hard to say, but in most cases there is actually reversed flow back there, at least closer to the top of the rear face - and, free stream pressure to boot. With the aluminum (or stainless whatever those happen to be) vents as low as they are in that car, perhaps there is actually a slight pressure drop and some air extraction from inside the engine compartment. I have not included internal flows yet in my analyses (CFD) and when I do, I will also be including heat. The heat alone will make a difference, increasing the pressure inside the bodywork a bit, and needing those vents as a bleed.
It would be interesting for one of the current GT40 owners to do a simple test - mount a taught, thin wire - vertically and set back from the rear face about 6 inches, set just off to the side from the exhaust outlets. Tie some very light strings at 3 inch intervals up the wire, and go for a drive with someone in another car alongside so they can take pictures. It would be really interesting to see what the air is doing back there on a 40.
On that note, does anyone here who is designing their own GT40 have a good 3D CAD model (solid model or maybe even surfaces - but not a simple AutoCAD line drawing) of the GT40 body? I could run some CFD analyses on the base body, then try front splitters, rear spoilers, etc... Anyone interested?