With a compression ratio of 13:1 with aluminum heads, approximately what octane fuel would you need to run? I have 114 octane readily available in my area. Do you think it would be possible to mix the fuel say 50/50 with 93 octane gas and not get detonation?

I'm wondering because I think I'm going with 13:1 compression and a pair of aluminum 360cc intake runner heads for next spring.

 

I used to do something like that. Your proposed mix would yield about 103.5 octane. The problem with race gas is it isn't full of stabilizers etc. So it's a mix and use concoction. Your can't let the stuff sit in your tank for a week.

I used to buy 55 gallon drums of methanol for about $100. It's @ 150 octane. It mixes up to 20% with gas and I ran it in my car and drag bike. It's down side is having to mix anti corrosion additives and it absorbs water out of the air. So it's another fill the tank and use it blend.

IMO - Your better off with less compression unless it's a pure race motor. The difference in power from 11/1 and 13/1 is only a 2-3%. So on a 750 hp motor your only talking 15 -22.5 hp. Those figures are also very dependant on the cam timing.

Endurance motors are also kept below 12.5 c/r once you get into the 13-15 compression range bearings and rods just don't last.

I run 11.2 and drive around with pump gas and my wallet is happy. If I want some additional boost I blend in some race gas for the track change the jets and timing slightly. Uncap my headers and give everybody that nice smell of race gas :seeya

 

Shane the cam has alot to do with it. Your cranking compression even with 13-1 can be around 175-185 and a lower compression motor with a mild cam can easily be over 200.
You will just have to try different mixes and you will hear the ping if it doesn't like it.
My 8-1 motor with 12 pounds of boost is running about 14.5 compression at that boost and I get by on 94 octane.
The cam drains low rpm pressure off allowing the motor to run fine and at high rpm you can get away with more compression, the cylinders are not filling as good.
I ran 11.5 fine on normal pump gas with a 256, 264 @ .050 cam and 108 lope centers.
You need the compression to make up for that wild cam you bought.