[DAVID GAGNARD]

Even with your compression psi being down to what it is,I don't think that would equal to the loss of hp your seeing,just my opinion......

Sounds like your dyno guy tried jetting and timing and got that part optimized to the engine,so taking that out of the picture,it has to be elsewhere......

Not knowing anything about the headers/sidepipes/mufflers other than the diameter,I'm betting there is a big loss there......I'm running 2.5 inch exhaust and 2.5 inch in/out big mufflers on my little 331 stroker and it is in the 400 to 425 hp range.....

Inside those 2.5 inch side pipes are mufflers of some sort ( a lot smaller than 2.5 inches) and I think that is a big "choking" point for a 427 stroker engine......I'm betting taking off the side pipes/mufflers will surprise you....For a 585 hp,427 stroker,I would run nothing smaller than 3.5 side pipes and a free flowing muffler to see optimum power...

Can you post of photo of the side pipes???

David