BlkO4Mach1

is 11.5:1 to high for reg 93 octane?

hotrod7687

Yes

Most ive ever been able to get away with is 10.0 to 10.3
You might be able to go a little higher on a carbed motor but you would have to retard your timing quite a bit for it not to ping.

BlkO4Mach1

my mach 1 had 10.5:1 that why i ask?

P Zero

I run 11:1 in my car with no pinging, regular 93 pump gas.
-P.

NORTON98

can you have PI heads and run 91 octane?

hotrod7687

10.5 might be ok too. Last 350 chevy i built had 10.7, we had to retard the timing to 8 degrees at idle so it wouldnt ping. It worked, but i know the motor had much more potential if we could have raised the timing.

We went to the track a few months later and got some race fuel, bumped the timing up to 12 degrees and cut quite a bit off his 1/4 mile times.

code3GT

I have 11.25:1 and I run 93.