Theres no beating, I like making power with iron heads now I know I can go buy an aluminum head that makes more power way easier and cheaper than grinding up a set of 915s putting in 2.18 and 1.81 valves but I enjoy the work and the reward. I've heard to no end you can't do that or it's a wast of money. I learned how to make power by reading everything I could then asking a few important questions. But 645 hp from 915 heads isn't bad for an old retired fart.