Depends on the altitude and octane but you are right for sea level pump swill. 340 I built in my Challenger many moons ago would run ok on 93 during the winter in Atlanta, but as soon as it got hot during the summer it would run on and knock like hell. Had to run octane boost. I also knew nothing about rounding the sharp edges and cleaning up the chambers back then so it likely would have made enough difference if I had.
