Thank's for the response.
If you dont mind I would like youre opinion on my situation and thought.
I am installing a turbo fuelinjected inline 6 in my '73 240z. The cowl induction theory wont be a performance robing issue in my eyes.
Now I believe that the induction could only ocur at lower speeds but even then the known positive pressure (high pressure area) in the engine compartment wouldent allow this. Most cars with cowl induction hoods have a small or almost no grill, unlike the Z.
The reasoning I am left with is, if the cowl isn't so great (large) to cause to mutch turbulence at the windshild the added volume to the engine compartment (from the raised center portion of the hood ie. cowl). And with the aid of the Bernoulli principle and posiably some reduction in the front grill. Then it will creat lower pressure in the engine compartment and give down force as the air is pulled out and over the car. As well as limit air from traveling under the car. The air under the car has more pressure than the air going over the car, making the air take the path of least resistance up and out. After all it is known that if you leave the hood unlached on a Z the hood will rise. This can't happen if youre induction theory is correct. In the case of a 240 Z I think there is somthing else going on.
Looking forward to youre response, Thanks.
It is all for the greater good of the Z.