The first question I ask folks that call me is "how does it do on the road at speed". If it does good at speed, but poorly at idle it is a fan/shroud combination problem. The "hold it in the radiator longer" theory problem is that you also "hold it in the engine longer". You cool it more in the radiator, but guess what happens to the water backed up in the engine.
If your racing you need a decent radiator, electric water pump, and electric fan with a shroud (custom tailor made prefered) that covers the entire radiator core. That is how you maximize your cars cooling potential, and eliminate aggravation.
The key is to do a better job of heat transfer (convection) using a nice shroud/electric fan combination. Then you can run the water thru faster and everything will be happy. I normally see 30-50 degree reduction at idle. Round-robin cool down 40 degrees less than 3 minutes. Here is what I'm using in my Corvette project.
Wade Mahaffey
