How reliable would an LS engine with aftermarket iron block, 4.185 bore and conventional or MLS head gaskets, NOT copper or o-rings? How much boost could such an engine run? 20 psi? Would that be an application for 6 bolt heads?
GM's own LSX 454 uses a 4.185 bore by 4.125 stroke, so the 4.185 head gaskets are shelf items. I don't know if those are conventional or MLS gaskets.
Yeah, 4.185 is a fairly large bore on a 4.400 bore center, BUT...
BMW S54's run an 87mm bore on a 91mm bore center, iron block. That's 0.157 between bores, which is like a 4.250 bore in a LS or Small Block.
Those engines run 11.3 compression stock and can be boosted enough to push an E36 M3 to 200 MPH in the standing mile. I *think* those engines use o-rings, though... maybe even siamesed o-rings. AND they only run four head bolts, but they have a pretty small bore.
ETA: Also a 4.250" bore small block, but not recommended for boost: http://www.hotrod.com/articles/454-s...-crate-engine/