What octane should I run?

[hotrodaj_2]

I posted this about a month ago and if 10 people replyed I got 10 different answers, so I'm asking a pro now. At what compression do you need to stop running 91 pump gas and start running 100 octane. Before I hurt it the motor had 155 psi comp. I will have more now after rebuild. I don't wanna ping. What do you suggest?

 

[yb200]

i would think anything over 160-170 you would want 110oct

 

[hotrodaj_2]

At 155 psi I was running 100 oct to be on the safe side. I know you can have to much octane also but I felt I was ok. I dont really want to run110-114 race gas unless I have to. If I have built this thing where it has to run on race gas then so be it.

 

[phragle]

155 160 your fine with 93 pump.

 

[hotrodaj_2]

My new piston rises higher in cylinder than old piston. I dont really know why yet, I noticed it after cylinder was on and didnt want to remove it again. Piston comes about 1/8 inch higher (doesnt hit head).Thats going to raise compression more than a little.