Are you only hearing what you want to hear?.. there's headporting gurus on here that prefer the speedmasters over the edelbrocks... For the price of the custom rockers you'll have to use and pay for to accommodate the trick flows you could buy a complete set of speedmaster heads that will accommodate your factory rockers... If you're building a 416 pump gas street engine there's almost no way of killing north of 400 horsepower...