The 360 ran great with that setup, considering it had stock dished pistons over .100" in the hole. Pulled this boat into the 14s, but developed a bottom end knock. I had the 318 laying around so I went through it and put it in. The 318 pistons are the stock flat tops, about .050" down. I'm thinking I put the timing set on a tooth off or something. It's gotta be. Everything else is the same, heads, intake, cam/lifters, pushrods, timing set, and carb. I can't think of what else it could be....