I run a 422 stroker (340 with a 4.00 crank) in my Demon. It has ported closed chamber iron econo W2's and 9.6:1 compression, runs great on pump 91. It all boils down to the piston and chamber details (quench build, hot spots, cam specs, etc.). A proper cam design that bleeds off a bit of compression can help with detonation issues.