I have a 383 LT1 with AFR heads, and a 240-242 cam. I wonder what timing (degrees) you guys are running at, with similar set up. When I put high octane gas (100unleaded) the car runs great, with 91 octane it chugs a bit on the low rpm. Since it runs great with higher octane, does it mean I need to pull timing out some?
Compression ratio is 11.5:1 if that means anything...

Thx-Goose

 

Do you guys understand my question?
How many degrees of timing do you guys run? Ballpark figure?

 

Are you seeing any timing getting pulled with the 91 octane?
You might have to much advance at lower rpms, sure.

 

with lower octane you would need to pull timing, higher octane you can add timing. Reason being is 100 octane will burn longer in your case, by adding timing you can fire the plug sooner & let the fuel start burning sooner cuz it will burn longer, with low octane you retard the timing because you want to fire later since it doesnt burn as long.


In your case what is happening is your timing is staying yet your fuel is burning longer, with this you are most likely creating more backpressure since you prolly the fuel burning in the exhaust still or close to it.