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Yet another idle-time brainstorm as I work on my FED build....

Wondering about using E85, which I understand had gained a fair amount of popularity.

For now (at least) I'll be running a Quadrajet carburetor (save the snide remarks please) and since it is a less than mainstream carb for drag racing I don't know if there's much guidance available for possibly converting it to run E85. One of the main reasons it seems appealing is it's cooling effect, much like running methanol. I will be running a small radiator but think it might need a bit of help. Also understand the E85 might offer a bit of performance boost. I just don't know where to start, as far as re-jetting, since my (limited) experience with methanol was with a Holley carb on a dirt circle track engine.

Any suggestions or info?


I like quadrajet,I've used them on drag and oval dirt and ice racers you will need the biggest needle and seat available the problem is the small bowl size have never used e85 you would have to play with the jets, needles and hangers  but i would try it   It's not the same a methanol

I have found a little bit of info since I posted about converting to E85. It sounds like about 30-35% larger jets are needed. I guess stock jets could be drilled out, probably drilling from the threaded, "back" side of the jet to have less chance of messing up the opening taper? What I found didn't explain what they meant by 30-35% larger. My guess is they're talking that much larger cross section of the orfice, which seems plausible. I wouldn't think it would be referring to 30-35% larger diameter; (ie from .060" to ,090") which would be a HUGE increase.

With my limited methanol experience I found out the hard way that slightly lean can get ugly really quickly. Is E85 a bit more tolerant of "slightly lean", or does it start burning holes in pistons quickly too?

I intend to first get the car going on 91 or 93 octane (I have about 8.9:1 compression in my 305), and then maybe try E85 after the car is actually running and checked out. I'd rather make baby steps and not have the whole program messed up from the get-go.



lake_harley - I believe your reference to the 30-35 percent increase regards actual E85 fuel flowing through the carburetor from idle to WOT versus 90 octane gasoline.  You are right it does not refer to a larger "jet diameter." The solution is not as easy as drilling out the two jets on your existing quadrajet carb to increase the "area" for more flow.

If you wanted to do this with precision, flowing the individual jets would be one method; for a mechanical fuel injection system that operates at higher pressure/flow than a carb jet, FIE has the setup to professionally flow individual jets.  It may not matter as much with a carb jet.  Drilling out existing jets to increase flow has been done by many others over the years in many different type carbs.

I've not sure how a quadrajet carburetor would run on E85.  As a starting point for your particular engine, I think the 30-35 percent increase means both in the primary and secondary flow.  Drilling out the 2 primary jets (i.e. increasing area) may only be a starting point.  As you know, there are businesses that sell new E85 4-barrel carburetors, and they sell for $700-$1000 each.  The new E85 carburetors do not resemble a quadrajet style carb, there must be a reason for this decision.

You mentioned methanol versus E85 and slightly lean burning holes in pistons.  I do not have much experience with the internal workings of a quadrajet carburetor and only somewhat familiar with how they operate.  For your idea of using a quadrajet carburetor for E85; if you were to only modify the primary side to increase fuel flow by 30-35 percent and not modify the secondary, I could guess you may experience a lean condition at WOT that might do damage.

My experience with methanol with a mechanical fuel injection system has been it tends to run richer as you go to WOT, and therefor in some cases a need for a high speed leanout.  Setting my tuneup with methanol, I have it set up very very lean to start so it can build engine heat quicker on startup.  Once you rpm up, go do your burnout and make your way to WOT, the system goes richer with mechanical fuel injection.  I'm guessing with E85 it would be similar with mechanical fuel injection, you will have to let us know how it works with a carburetor.  Alan

a carb has a constant fuel pressure were as mech. fuel has increase in pressure and fuel as the rpm increases so a carb might go lean if the pump can't keep the bowl full and in a quadrajet it's the needle  seat that doesn't flow enough. quadrajets were used on motors as big as 455, 454 and 500's nicest street carb, for racing you have to have access to special parts maybe with the internet it would be easier


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