radiators in race cars should only be as big as required to keep the engine cool. Any more than that is simply extra weight you have to cart around, and its at the extremity of the car which is the worst place to carry weight.

Alot of the guys who responded above have done engine swaps, and an A series engine won't need rads that big.

My car (L18 1995cc, Volvo 244 radiator)overheats on the racetrack with the front spoiler off, but runs perfect with it on. That's another way to improve your cooling system efficiency, especially on race cars.

Cooling efficiency is improved because the front spoiler eliminates alot of air from flowing under the front of the car, creating an area of lower pressure behind the spoiler. This allows the hot air in the engine bay an easy escape path out under the car, improving flow through the radiator and lowering underbonnet temps as well.

The front spoiler and resulting lower pressure under the front of the car at speed, also makes the car more stable by reducing lift.

So they are a very good idea for race cars. Attention has to be paid to brake temps and ducting though.