In my experience, aiming for a HP number has always left me feeling let down. Maybe because the engine builder I use has a dyno that doesnt produce the big numbers. I like Dwayne's take on it, that the power will be what it is. My car has a 505 with stock Stealth heads and a comp XE 284 hydraulic flat tappet. This car/engine was built by someone else and their dyno showed 550hp. Seems a little high to me, but im sure the previous owner felt good about that number. I'm replacing the Stealth heads with TF 240's and I would hope to see near a 50hp difference...but I would not expect to see 600hp on the dyno. Not on my guys dyno at least.