I'm running 452 castings with KB flat tops about .009" out of the hole. Closest I can gather I have approximately 10.7:1 as I didn't cc the chambers. Cam is 228/236 110 lsaTQ50. I've never been below 3000 ft elevation and I have the timing set at 38 total. Pushing 5000 lbs 4x4 it runs 87 octane at 5500 ft all the time. I did put premium in it at Vegas though. Did not hear any signs of preignition. Running cold plugs, they'll load up when the engine's cold. Also ran 11.2:1 in a 408 in the same truck at 900 ft elevation. 231/237 and 110 lsa. It would rattle now and then if I loaded it in third or fourth below 3k rpm. Aluminum edelbrock heads opened up to 68 cc's. Surprisingly the open chamber 440 seems to be more detonation resistant than the .038" quench small block was. Granted, not apples to apples as the 408 lived at 900 ft and the 440 stays at 5500. Never did a cranking compression test.