9:1 compression and pump gas octane

[Mr URL]

I shaved my heads to remove the old ring gaskets you can't get anymore and went to single shim gasket from RJC. Compression is about 9:1 give or take. I used to be able to shoot some 91 octane at 10 psi before the alchy came on. Seems like that's not an option now. But with 93 octane I can push 20 psi with a few degrees retard with a 91 octane chip! Only 15 degrees timing. So just confirming if running 9:1 or higher 91 octane is not an option anymore. It's more like 93 octane and alchy.

 

[Turbo6inKY]

Running these in any capacity beyond base OE tune and configuration with 91 octane is a gamble.

 

[BEATAV8]

less timing and richer AFR.

 

[HalfDozIN]

I once ran 10 psi in mine on 87 octane with 18 degrees of timing and had zero knock, although I have a measured 8.5:1 static compression to your 9:1. Still, I wouldn't think 10 psi would be any problem for 91. What was the air/fuel ratio?

 

[Mr.Spool]

What needs to be considered is when you don't get 91.
Low timing low boost and a fuel cushion is a must.
If that 91 gets cocktailed out with some 87 it will detonate