So I'm thinking about building an E85 motor. I live in the corn belt, there's E85 at the pumps all over the place. The closest one is 5 minutes from my house. I know I will have to make sure the carb is up to the new fuel, but I don't think that's going to be a huge problem. I'm going to have to re-do a lot of things when the LG4 finaly comes out.


But, I'm wondering what kind of comression I can use with E85. The motor I'm (currently) thinking about building is a 355, iron vortec heads. Flat top pistons(+5.00cc), and a hydraulic roller with 218/224 duration at .050, .330/.335 lobe lift runnning 1.6 roller tip rockers for .528/536 valve lift. Intake closes at 64 ABDC. With a .040 gasket and .025 deck height I should be a 9.8:1 SCR and 7.74:1 DCR. From what I've read this is slightly over the recommended 7.5:1 DCR for pump gas engines, but not necessarily unreasonable. FYI, I want the engine to have it's torque peak at ~3500, in order to use a reasonable stall converter for the street.


What can I get away with running E85? I know 9:1 DCR is a good target for race fuel engines. Isn't E85 something like ~100 octane? So, if I went with slight dome pistons(-4.00cc) and a thinner .030 gasket I would have 11.17:1 SCR and 8.81:1 DCR. Would that be a workable street combo? What if that same engine saw E70, which is what the pump ACTUALY sells in wintertime because some engines need the extra heat from the gas to run in cold temps. Will hypereutectic pistons work with this much squeeze? How about properly straight stock SBC rods?

 

My engine runs at around 8.3:1 SCR. 7.5-8.25 is ideal I think for a street car. So dont fret over 7.75. If you were at 8 even that'd be even better. But at 7.5 you'd be able to run regular unleaded very easy probably.

I dont know much about E85, but I do remember reading several times that the sky was the limit as far as compression ratio with them. 11-14:1 SCR is no problem for them. The problem is that as far as a performance ethanol motor goes, there just haven't been enough people to try it for there to be decades of established rules of thumb and guidelines to follow to make it work the best. In a way you'd be on your own.

You do need to do a little research, there's a lot of controversy about what all needs to change, but generally your fuel lines and pump should be fine, it's just a matter of getting your carb tweaked right, if you can do that without buying an E85 carb.

 

"The 105 Octane of E85 is very nice, but with the added cooling effect it makes it perform more like 115 Octane Racing Gas.
There are guys running 16-1 compression ratio NA with E85, and NO pre-igniton."

Some good online info around

"No matter what type of fuel system you are running you must increase flow (volume) by roughly 30% over a (gas) setup.
This is more than just increasing the main jets (in a carburetor) by 30%. Flow must be increased throughout the whole system and fuel curve."

May have to re-jet carb between winter and summer fuels
http://horsepowerinnovations.com/tuning_tips.html

 

I am shooting for 11.4:1 on my 5.7 Hemi Ram that I am setting up to run on E85.

 

An interesting angle of E85... since it needs more compression than a gasoline engine, you can always build a more traditional gasoline engine, and then use E85 and boost it. It'll get you the leeway you need to turn the boost up a good ways I bet...