As usual, "IT DEPENDS".
I'm running a 400-based 462 with ported O-port 72cc E-heads with the "fast-burn" chambers. My block is zero-decked, and I'm running 14cc dished pistons, Fel-Pro 1016s. After the valves/seats were all done, the chambers were cc'd and the actual SCR is right at 11.0:1. Cam is a CC HR with 238/248 on 112 and about .650" (QNI lobes) with 1.65 rockers.
During break in on the dyno, and subsequent intake testing, we ran 92 octane and now that the engine's in the car, I run 91 octane non-ethanol. 34 degrees of total timing with about 16 degrees of vacuum advance.
I'd still be OK at 11.3-11.4.
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