The Stovebolt Site Forums The Shop Area Engine Shop Carburetor Modifications for E-25 Usage

To All,

A friend of mine in Brazil is running a GMC truck, with a 270 and the stock Zenith 28AV11 carburetor.

Apparently, almost all of the available fuel down there is E-25, so he is looking to make the appropriate modifications.

Main questions to the carb gurus out there: Is it possible to recalibrate his existing Zenith to run on E-25?

Since the stoichiometric A/F for gas is 14.7:1, and ethanol is 9:1, and if my SWAG estimate is correct, I figure that right off the bat the original jetting is around 10% lean. Assuming the appropriate parts are available (or can be made by modifying existing parts) Is the Zenith design robust enough to accommodate the additional fuel flow?

Also, since ethanol has a higher specific gravity than gasoline, will any other internal settings require modification? Float level, for example?

Are there carburetor shops that specialize in these types of conversions? If so, how do the typically ensure that the carburetor is delivering what they expect? Do any use specialized equipment like a flow bench ? Or will I just have to borrow a 5 gas analyzer and ride out next winter down in Rio ?

Even if this particular model can be setup to provide the correct A/F ratio, are there other considerations — like material compatibility with a fuel containing 25% ethanol?

Is he better off just possibly looking for a suitable E-25 compatible replacement carburetor — assuming one even exists?

I would welcome your thoughts on this, especially if anyone has tackled such a conversion in the past.

Best Regards…