Hey, VingI'd like to suggest that by looking only at HP you ignore the effect of the realtionship tween power and weight.
Bee for your bonnet: instead of looking at how cars of different HP counts behave, take a look at how cars of different power/weight ratios behave.
I think you'll be pleasantly surprised by what you find out about the cars you test, regardless of their HP.
PS: See if you find a P/W number that leads you to think a car will be a successful racer. Someone else already mentioned on this thread that they like 2.700 or thereabouts.