Im using my old 305 heads on my 350 block, which makes around 9.75 compression with the rest of my motor specs. what grade gas do you guys think i should be running?? do you think i could get away with 89 octane? or no. i've been running premium, but its getting a little pricey so i wanted to know if i could bring the octane down safely. i know im probably going to have to change my timing as well.

 

Do a internet search and then a little research on "water injection"

With a simple water injection system you very likely can run full timing without knock using 87 octane gas.

Water injection typically improves the apparent octane performance of a certain grade of gas by about 3-4 octanes.

 

Wow, that is very interesting. I haven't heard anything about that. With my vortecs, I'm expecting about the same(9.8). I wonder if anyone on these boards are using that?