I have a lq4 and I'm waiting to do a 12.1 compression can I do this on pump gas or do I.have to have 110.octane , if not what the highest compression , I can run on pump gas?

 

Your cam selection has a great deal to do with this, read up on dynamic compression ratio and go from there.

 

On my 408 I'm running 12.5:1 dcr, but 8.22:1 dcr with my cam (255/263 .624/.624 115lsa) on pump gas with no problems.....full 26 degrees timing and 0 knock spinning to 8,000

From everything I've searched and read 8.5:1 dcr, and about 200psi cylinder pressure is about max for pump gas

 

12.5 is pushing it on pump gas, your not going to get that much timing out of it. Less timing less hp. 8.5.1 cp is nothing. Once yuou start getting over 11.5 is where it gets tricky.

 

Sorry, typo...damn auto correct...12.5 Scr, not dcr.....8.5:1 dynamic is max for pump gas.

When running a bigger cam you need to raise your static compression to keep your dynamic compression up.....the later your intske valve closes the lower your dcr will be.

At or over 8.5:1 sec is where you will hsve to start pulling timing and still might have troyble with knock on pump gas.

 

I've run 12:1 and 9 DCR with no issues on 94 octane.

 

92-93 octane around here and I have always questioned having one pump nozzle for 87- 93....there has to be some cross contamination...I'd think

 

Why?

Do you plan on driving this on the street? If I were you I would stick with 91 Octane fuel. Many pumps DO NOT have 92-93+ octane. Places like Utah barely have 90!