A freind of mine is building a high comp and cammed motor. How do you know what the octane rating should be? Do you just try various levels or what? And do you want to run the lowest octane possible or run it higher than needed?

 

By Running a fuel with to low an octane rating you can cause detonation which will lead to major problems. The higher an octane rating the slower the fuel burns. The best octane is the lowest you can get without causing pre-ignition. Try some vp c12 mixed 50/50 with 92 and test her out.

 

My understanding is that with a compression ratio of 11 to 1 or higher, race gas is necessary. If the ratio is below that, he may get by with 92 octane, so it would be wise for your friend to determine exactly what his ratio will be.

 

With 11:1 you can run 93 octane just fine. I know a couple people that do. Above that, yes you need to run a higher octane fuel like race gas.

 

Thanks everyone.

How do you know how high to go? I know if you go to high you will lose power.

 

Something else to keep in mind is the higher the rating the cooler your engine will run.

 

Ben,

What compression ratio are you looking to run.?