Ive been here a long time, i just normally read to myself. But i couldnt find a positive answer for this question. Im working on a 27 magnum, rebuilding the engine. I am at the point of ordering my cam, but i dont know what i can get away with as far as exhaust duration goes. I know with normal manifolds they say dont go over 230 @.050 on the exhaust side. Will that change if i am using the 496 manifolds? If it does change, what is my limit? I wont over cam the engine, but i love big choppy exhaust notes. The rest of the engine will be built accordingly. The rest of the engine is pretty simple, all forged rotating assembly, balanced. 10 to 1 compression with large rect. port heads with mild port matching and bowl blending. The cam will decide my intake, but it will be a performer rpm air gap or a victor 454r. I would like to be able to spin it up to 6k, and that is why i am having to ask now about the cams. I am not new to building engines, but i am new to building a high performance engine for marine use. Thanks for any and all help