We're looking at Sunoco 116 octane . . and
coolracing was pretty close to correct . . "RON" and "Motor Octane" are two different things as are "oxygen content" . . Which, in the case of the latter, DOES change the energy output of a Fuel . . Something that I had been led to believe didn't change with octane ratings in gasoline . . Exactly how much it changes BTU's (Energy output of a fuel) isn't shown on the chart (
http://www.racegas.com/fuel/compare) but it has to . . Because that's what "Oxengenated" Fuels do . . BTU's have to change as the burning of the fuel increases/decreases. How much might be another debate . .
Point is, in our case, we probably need more compression than we currently have, if we're going to run at high altitudes . . Old rule of thumb: "If you have no air, you have to make some" NASCAR whizzes
make air in restrictor plate racing by upping the compression in some cases to 17:1 (just one of many of their "secrets") . . But, we also go down to lower tracks sometimes and really can't afford to run two engines . . Christ, it's a bracket car! Sooo, we "Bump the Lead" to up the compression when on the mountain, and back it off a bunch when running below 4800'. Thus, Octane has a lot to do with the up high situation . .
That's my take on all this, but there's some of you up here who have messed with normally aspirated BBC's a whole lot more than I have . . I'm listening . .