E85 with Roots, What Compression?

I asked this of one of the local engine builders, and he wasn't sure.

The Methanol guys run +11:1 with a big blower....

What would you run on E85 and a roots blower? What would target boost be?

I run more compression on race gas

I mulled over this question for a long time, read everything I could and talked to several people I respected. I settled on 11.5 in my 413 smallblock. E85 with a 6-71 and mechanical injection. Haven't run it yet but I'm getting very close.

I went with custom dished pistons and thick cometic gaskets. I went this way so that if I didn't like the blower setup it wouldn't cost a fortune to put thinner gaskets on it and have fair compression to run race gas.

I think 10.5 would be good with E85 and it is not as forgiving as Meth1

I would determine how much boost you want at a specific RPM and then decide on how much mechanical compression to start with, regardless of the fuel type

The higher the CR,the smaller the tuning window........
I went 9:1 on gasoline.But I still street drive.

That's what I was thinking. If I do somthing different this year with the G3 parts I have been picking up, I was looking at a 671HH and E85 with 2-carbs....11.5:1 I figured would be a good starting point but can't find any info on anyone who has done it...Most are running either straight Methanol 14-71 hi helix or a street car on gas.

This would be race only, but I wanted to see if there was any difference between the Methanol setup and E85...I was also wondering how high can the boost be pushed....Figured, why limit it like a street engine...its alcohol right....

If you can control the spark, 20 psi is fine.
You haven't said what the blower is capable of - its efficiency range. "Roots" covers a lot of sizes and designs.

You can run 11.5 to 12.5 mark sullens builds a great e-85 carb or mechanical injection from kinsler have them flow a system. I have seen 40lbs of boost with e-85 you will love it.

^^^ Yep go ahead and do that.

If its race only, why bother with carbs? If it is strictly a race engine, then put a bug catcher on it. Cost wise, a pair of new E85 blower carbs vs. a good used bug catcher setup might not be that far apart.

I think it was his carbs on my buddys E85 440 with 671, and man it runs hard! Not to mention it has a nice clean idle...






As you know, I have had a Bug Catcher system. To be legal I have to run carbs or mechanical FI....I am not one for all the issues those guys have with MFI and there are no manners to it either. We will see what this season nets us...The Big Hemi is back together, and I have one last issue I need to fix, but its ready to run. It will be for sale, and I am switchiing....Its funny how many guys told me so far to put a Chevy in it.

What are you looking to make hp wise?1600?That would take some big carbs.

we can get these up to 1600 cfm
1750 cfm with a little extra shaft and booster work

top view

$$$$$

Yeah, how much are those bad boys.

$1,500

I too will be testing a twin for my Dart here soon and if it performs as well as the claims, I will be selling these for Get-M Garage just like Mr. Baldwin..............

🤙