Cylinder pressure due to fueling and timing, not boost, is what dictates the need for O-rings.I'd like to jump in here if I may. I also don't want to derail the current discussion, but I think my question may be relevant. I'm contemplating compounds on my truck as well and have a good idea of some of the required upgrades, such as head studs and clutch. I already have 5x.011 DPP injectors and a 4" straight pipe exhaust, as well as an HX35 turbo.
My question is whether or not I need to o-ring the head. I spoke with tech support at PDD and he said that, because it's a12v, I need to o-ring the head for long-term reliability. His explanation is that boost pressure rises much faster with compounds than with a single (I understand how compounds work, so I'm good on that part) and it will cause a blown head gasket over time. It sounds like good logic, but does this seem reasonable? I hear of many compound setups, but no one ever talks about o-ringing the head, just head studs for the extra boost. I'm planning on a 450-500 hp build as a daily driver with towing in the future. Any input would be greatly appreciated.