Is weight a factor in your build, for some reason? Aluminum heads will transfer some of the power you're making to the radiator instead of the rear axle, sucking up that thermal energy and blowing it away with the fan instead of using it to shove the pistons down the cylinder bores. Doing race car stuff on a street engine usually doesn't have very good results.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!