I am starting a new engine build. I would like it to make the power on pump gas. I have heard of people running upwards of 12.1:1 compression on pump gas with coated pistons and combustion chambers. Has anyone done this or had any experience with it?
Thanks,
Brit

 

What heads? What are the piston specs? Camshaft specs? What size engine? EFI or carbureted?

Need to be much more specific before you can get an accurate answer. There are LT1 guys running as high as 13.5:1 on 91 octane, but some guys have knock issues with only 9.5:1 on the Gen 1 engines.

It all depends on the combo.

 

Your static compression ratio is pretty much meaningless when it comes to your question. What you need to worry about is dynamic compression ratio.... It's all about your cam selection that will decide if you can use pump gas or not. In theory you could run 15:1 on pump gas if you had the right cam to yield a low enough DCR... Of course the engine would probably not perform very well.

Give this a read: http://www.empirenet.com/pkelley2/DynamicCR.html

 

You are correct, I should have been much more specific. Aluminum vs iron, bore size, etc. I understand that with a larger cam you can run more compression on pump gas because it bleeds off cylinder pressure. Is there a calculation that can be used to find DCR. By they way, great article.

 

Coated with what?