Octane and timing..

[MrobsMan]

If you're pushing the limits of knock, use the highest octane you can get. Detonation is engine death, btw. I'd be setting a stock engine to stock specs.

You wanna run the lowest octane possible without knocking to make the most power possible

 

[Komet]

You wanna run the lowest octane possible without knocking to make the most power possible

The specific energy of gasoline is not affected by its octane rating. Octane is essentially 'knock resistance'; the higher the number, the more your fuel will resist detonation before it's party time.

Perhaps what you're thinking of is that you want to run the highest timing possible to make the most power, which is true, but there becomes a point where the juice isn't worth the squeeze, because you're edging closer to the limits of detonation for very little power gain (1-3hp). Your motor might be perfectly fine with an extra 2-4 degrees of timing, especially if what you're really doing is compensating for slack in the timing chain, but you should test it 2 degrees at a time and start out with as much knock resistance as possible to stay safe.

 

[Erik the Awful]

The specific energy of gasoline is not affected by its octane rating.

It depends on what they're using to get a higher octane. If they're using ethanol to raise the octane, you don't lose any significant horsepower. I don't know what effect MTBE or BEX have on the power output, but I know back in the day guys were dynoing engines with 87 octane and 91 octane and could see a difference.