[Ron61]

What 52chevyred said is all true and good. And the more pressure that you run the cooler your engine will run. But don't go to far unless you have had your radiator pressure checked for the higher pressures as most stock radiators will start bursting seams at around the 18/20 pound level. I think NASCAR used to run theirs at around 25 pounds but they made them lower it. That is why you will see so much water coming out the overflow hose they use instead of a recovery tank. Al, the cap does is determine at what pressure your radiator will start to push water out.

Ron