A new set of pistons from Diamond with correctly placed and sized valve notches for your cam and valve gear that you have is a lot cheaper and more effective way to fix your ride. You may not have enough meat in your current pistons to safely cut deeper valve notches. Diamond warned me about the chambers in the Victor heads and spec'd my piston domes/valve reliefs accordingly. No problem whatsoever with 280*/283*, .690" solid roller cam. Call them and plan ahead for future valvetrain changes. Won't cost anywhere near that $4000-6000 price tag you spoke of earlier. The clay don't lie if it's done right,as you found out. Add a good top ring and a little extra gap and you could also spray some safely and make alot more power than a new set of heads- for less money. You got a great project. Good luck. Jeremiah has made some great power with those Victor heads. Send him a PM. I'm sure he would share his experience. He's a real nice guy. Bill