I'm working on my 455 buildup but still needing some answers. I'm looking to hit 10:1 with AL heads and give 450 hp streetable and pump gas. At how much valve lift would I see an interference problem with the 10:1 sealed power forged pistons with a zero decked block, if I were to zero out the block? What rocker ratio should I be using? I have a set of stamped steel 75 ones and would rather not replace them however, If i need to I will and what ratio are the 75's I know a lot depends on the cam but I want to have the options open for any decision.
If you want to have the options open for any decision, you need to have the valve reliefs cut in the pistons. You also can run into trouble with camshaft lifts greater than .500" with stock rocker arms, they don't hold up to the extra pressures required. It's always best to check piston to valve clearance, even if you don't think it will be a problem. The lift isn't usually the problem, its the duration that can cause interference problems. The top of the piston is no where near the valve at full valve lift. The problems happen when the intake valve opens to early or the exhaust valve closes to late. The stock rocker arm ratio for the steel rockers is 1.55. Aftermarket rockers range from 1.6 to 1.65. I personally liked the 1.65 ratio best. The valves open and close faster and a little more lift is achieved while duration remains the same.
