I replaced the pans on both of my cars, and it's amazing how much the air flow through the engine compartment increased.
My 29 CCPU has a 4 blade fan, and even at idle, you can put your hand in front of the radiator and actually feel the suction of the air flow, as well as feeling a breeze flowing out through the vents on the sides of the hood.
Yes, they can make it a little pesky to work on some bits and piece under the hood, but they are fairly easily removed and replaced for major engine work.
Also, I live on a gravel road, so they STILL perform their original function of helping to keep dust and crud out of the engine room!
