don't know if this has been covered before, but are you sure it is detonation? maybe an exhaust leak? just throwing things out, but i guess you said it did go away with the retarded timing.

maybe it has more compression than you think? even with the new cam bleeding some of that off, it isn't enough?

don't know... i know comparing a hemi and a wedge isn't a real comparison, but i'm around 10.25-10.4:1, 210 psi hot cranking, and i have yet to hear the thing ping.