[Mcronk]

Back when I was racing my 67 GTO I tested a Ram Air pan at the track on back to back runs. I did have a open scoop and removed the hood bracing per the factory instructions. I picked up almost a tenth. I had kept very detailed records of each mod I did and would test several times to see if I could confirm the results. That set up was consistent for at least half a tenth to almost a tenth. I don't believe it actually provided a "ram effect" but did seal out the hot underhood air and allowed cooler outside air in. My opinion is the cooler air was the reason for the performance gain. I also had a carb spacer for this testing and had to trim the foam gasket in half to get the hood to close. So I had a very tight seal to keep out the hot underhood air. That setup used the standard 14 inch HO air cleaner with a closed lid. I wanted to try one of the open lid designs but never did. However I have heard that the open lid designs do not work well on Holley carbs but are ok on quadrajets. I agree that the smaller diameter air cleaners are going to be more restrictive. There is less surface area for the engine to breath through.