What is the highest compression ratio that you can run on an Olds 455 with iron heads and 91 octane?

 

Depends on your cam, which dictates cylinder pressure. On 91 octane, prob 10:1 with a decent cam. I can probably get away with 93 in my 10.6:1 engine, but the cam is 232/232 on a 112, engine cranks 190 psi. I run a race gas blend. We pulled it with nearly straight Shell 93 on the dyno and saw negligible power change from vp110.

 

That should tell you don’t need the 110 then.

 

Correct, but pump gas isn't consistent, and even the dyno guy admitted that whatever 93 fuel his local Shell sold pulled better than most other fuels people brought. For example, I brought 93 with me from a Speedway, and the engine ran like complete crap on it. So blending in some race gas blend provides some consistency/margin...