I know this thread concerns street cars but here are some aero stuff you might see at the race track.
The least amount of air flowing in the engine compartment the better.
Race teams have perfected blocking off airflow into the engine compartment with duct tape. Engine and oil temps are controlled at least partially by overlapping strips of duct tape over the grille opening and oil cooler opening. If temps are a little warm, a strip of tape comes off.
If temps are too cool, another strip goes on. This is something that can be done during fast pit stops without opening the hood.
At racing speeds hoods push up in the middle, hoodpin areas become concave, back windows blow out. I've seen windshields pop out of cars that spin.