E85 Street\Strip build??

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aengineguy

aengineguy

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I am considering building a 408 to run on E85. Could not find too much on this forum, unless I searched wrong. Would like to go with 12 to 1 on the compression??? The engine will have forged crank and H beams, aluminum heads flowing in the 300 cfm range.

I have read lots on the fuel system changes and upgrades.

Words of wisdom are appreciated!
 
With the high compression to get the benefit of the E85 high octane rating, I think you could go even higher CR. I don't know for sure on a street engine, but maybe 14 to 1. Consider a MSD dizzy with a retard feature to ease starting.
 
You'll need to run at least 12.5:1 on the CR and you'll need an alchohol compatible fuel pump and fuel lines. Quick Fuel makes an E85 specific carb that I would choose if I were to go this route.

Another thing is that alcohol makes reading plugs a *****. I would get a wideband Innovate A/F meter to get it tuned.

I contemplated doing a similiar build years back but nixed the idea when I realized that E-85 stations just were not catching on here in Denver and that stations were far and few.
 
Ramcharger...what kind of issue, if any, am I going to have with sealing on the head gaskets with those high CR's. I plan on using the good bolts\studs??
 
Not with a decent head gaskets and studs. Cometic!
 
I don't think you need to go that high on the compression. E85 is about a 106 octane rating so 12-1 is good. None of the factory E85 flex fuel vehicles run that high and they run fine. I do know that Mopar uses a special oil, fuel hose, fittings and bearings for the flex fuel vehicles because of the corrosive nature of alcohol.
 
Guitar Jones said:
I don't think you need to go that high on the compression. E85 is about a 106 octane rating so 12-1 is good. None of the factory E85 flex fuel vehicles run that high and they run fine. I do know that Mopar uses a special oil, fuel hose, fittings and bearings for the flex fuel vehicles because of the corrosive nature of alcohol.
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I've read (but have no personal experience) that an engine built for 12.5:1 and a relatively stock cam (daily driver) will run great. If he's thinking of going to a cam with the duration in the 240's @ .050 for street and strip use on that 408, I would think that 13.5 would be reasonable for aluminum heads.

In reagards to the flex fuel factory stuff running OK at lower CR's, I agree, but they have to run on both gas and alcohol so they don't have a choice.

What do you think Guitar?
 
No not really but it's just harder and more expensive to do. No off the shelf pistons unless you have a really small chamber head.
 
Guitar Jones said:
No not really but it's just harder and more expensive to do. No off the shelf pistons unless you have a really small chamber head.
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What about RHS closed chamber heads, some head decking and KB744's? The RHS head is supposed to have quite a bit of meat on the deck..
 
Well with a 4.03 bore, 4.0 stroke, 55cc chamber, .040 gasket and a 0 deck with about 6cc of valve relief you'll only get 13.0. You could stick that piston out of the block .010 or .011 and you'll get about 13.4.

Those RHS head chambers are about 62cc if I recall and they aren't aluminum either. I don't know how much you'd have to take off to get there. My small chamber W5s started at about 54cc, cut .050 off them to get it down to 47cc.
 
Guitar Jones said:
Well with a 4.03 bore, 4.0 stroke, 55cc chamber, .040 gasket and a 0 deck with about 6cc of valve relief you'll only get 13.0. You could stick that piston out of the block .010 or .011 and you'll get about 13.4.

Those RHS head chambers are about 62cc if I recall and they aren't aluminum either. I don't know how much you'd have to take off to get there. My small chamber W5s started at about 54cc, cut .050 off them to get it down to 47cc.
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Thank you Mr. Jones. I didn't do the math but I thought that magnum chambers were 58cc to start. There's no way for me to know mathmatically what the chamber volume would be at a given deck without much more information. KB gives 5cc for that piston and I also did not check the bore on a .040" thick cometic gasket, which really makes a difference too. As I always say, a true measured comp ratio is the only way to know. On my 4.0L build the factory specs were 62cc but with only .007" off I measured it at 58cc with an Autolite 985 plug and stock valves with a nice 3 angle and the seat on the intake moved out to the outer 3rd (.050" from the face).

As you and I both know, it depends on the limit we want to take it and the ability to make it so. :read2:
 
I could have gotten almost 15:1 on my new short block with a flat top .007 out of the hole but chose instead to keep the compression moderate at 12.3:1. It should be a bit easier on the bottom end, especially the wrist pins at idle speed and on the head gaskets that way.
 
So whats the highest compression you could have your
motor run on e85 safely without pinging?
 
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