It has been proven in the wind tunnel many times that a forward facing hood scoop really doesn’t receive much ram air effect unless it is extremely high above the level off the hood. I have a 6” six pack glass hood on my dart and saw no appreciable difference in performance on or off (not sealed to the carb though). I did notice the engine ran warmer with it ON. I would guess because it disrupted the air moving through the radiator as said above. This was on a mild street strip deal not a full on race effort. On our bonneville cars rear facing scoops always perform better than forward facing and naca ducts work even better
