Those cars(A bodys) are noterous for that regardless of the scoop type or size, it is the air pressure from the front end coming into the engine compartment trying to blow the hood off, not the air coming into the scoop Put a carb. plate on it to seal the air from the bottom of the engine compartment and see if that helps, I would block the air from coming in from the grill, it will come in from behind the bumper and up from the K member area also A good spoiler mounted in front of the radiator core support will help also My tube chassis 1970 Cuda has issues also but I have not installed a spoiler or carb sealer yet It trys to blow the hood off at 135+ MPH also on the throttle stop it is worst at 145 MPH off the throttle stop I need to block the grill off and install a spoiler also