I have a 5.3 with a 76mm turbo mild cam bigger fuel pump and injectors, my question is can i run 87 octane with 8psi and a conservative tune or should i just go with 91 or even e85?

 

Why risk anything?

You'd likely have to drown it in fuel or run like zero timing to be knock free on 87 octane. Run 91+ to keep it safe and spend the extra 5-8 dollars a tank.

 

Yeah it will probably even get better mpg on 91 and make more power

 

I doubt that it will get better MPG, but it will have a better chance of survival, and the window to make more power will be there. You could always hook up a meth kit as well, if needed

 

Running 87 octane in mine lol. More of an experiment to see what I can get away with though. However I already know my setup is very knock resistant, so it didn't exactly get 87 on a whim...

 

What makes your setup knock resistant, oh Mr. No Signature?

 

Quench, tumble and low compression.

 

 

I have been wondering if my new pistons are too far from the heads to give adequate squish at my compression (10.5:1). My old setup at 10.3:1 didn't knock, the new one rattles at around 4000 rpm. It goes away with a 50/50 mix of 93 and 100 octane.
To the OP, be careful!

 

What’s your quench?

My 370 is .045

I was wanting mid to low .040’s, I was less concerned with a billet rod. If a stock rod then that’s a bit different. My current motor seems to be less knock prone and it’s 10.0-1 vs 9.4 on the old.