For the general public, E85 is seen as a home-grown (i.e., not imported) alternative to gasoline, one that may or may not cost less and run cleaner than good old-fashioned petrol, depending on who you ask. Performance enthusiasts, especially those in the Midwest where the stuff is easily obtained, havelatched onto E85 (which is 85 percent ethanol and 15 percent gasoline) as a low-buck, high-octane alternative to high-priced premium gas or race fuel. But what does it take to make a carb E85-ready? As it turns out, the process is surprisingly simple, as we found when we installed Quick Fuel Technology's Billet Metering Block Conversion Kit, along with a few other necessities, in a Holley 750 double-pumper.
"The big selling points are E85's 105 octane rating and cheap price when compared to race gas," says Quick Fuel Technology's Shane Montgomery. Users span a broad range, according to Montgomery, consisting of performance enthusiasts, circle track racers who are tired of the price of premium gas, street/strip guys, and weekend bracket racers, among others. "You can run a higher compression motor and not have to pay $6 to $8 a gallon for race gas," Montgomery continues. "It's also a cooler-running fuel, so there's power to be gained."
So what does it take to make the switch to E85? In general, any carb and fuel system modifications must do two things: inhibit corrosion and increase fuel volume. On the first count, material choice is critical: brass floats as opposed to plastic, stainless steel needle/seat assemblies, and so on. On the second, QFT's conversion kit instructions say that running E85 requires 25 to 30 percent more fuel than gasoline, which in turn requires increasing the flow in all areas of the carburetor. And those two things, along with the necessary jetting changes, are exactly what the Billet Metering Block Conversion Kit and complementary parts accomplish.
While Quick Fuel can certainly hook you up with a purpose-built E85 carb-it's got eight different part numbers available-the kit can work just as well for the die-hard DIY'er or someone who has an existing carb they want to use. "The process is pretty straightforward," says Montgomery. "If the kit is installed by someone who's carb savvy, a conversion kit-equipped carb can run as good as a full carb." Just how straightforward? The changeover took us less than an hour, including time to take pictures. Of course, being carb-savvy means that there's also some tuning to do, and dialing the new setup in will certainly take more than an hour. The conversion itself, however, is surprisingly easy to accomplish-check it out.
Beyond The Mixer
Of course, converting to E85 means more than reconfiguring the carburetor-the rest of the fuel system must be tended to as well. According to Montgomery, you'll need higher volume pumps and fuel lines. QFT recommends an AN-10 line from the tank to the regulator, and an AN-8 line from the regulator to the carb. All should be braided stainless or hardline; there should be no rubber at all. The regulator should be set at the carbureted norm of 6 to 61/2 pounds of fuel pressure, and the pump should be capable of producing 250 gph. Lastly, paper fuel filters are a no-no when running E85; go with steel micron in this area.
What We Did
Convert a Holley 750 double-pumper to run on E85
This switch is surprisingly easy to do
Quick Fuel Technology's Billet...
Quick Fuel Technology's Billet Metering Block Conversion Kit includes two E85-calibrated metering blocks along with new gaskets, vent whistles, and fuel bowl bolts, all for about $125. QFT recommends also installing one of its alcohol rebuild kits (which contain corrosion-resistant parts) when installing the conversion kit in a used carb; given the $40 tab, it's a cheap enough way to ensure that all the carb's internals are up to snuff.
Comparing the stock and E85...
Comparing the stock and E85 blocks, the four emulsion bleeds are precalibrated, from top to bottom, at 0.028 inch, blank, 0.028 inch, blank. According to QFT, this setup will work for most engines with a properly sized carb. It's actually calibrated to decrease the amount of air that mixes with the fuel; experience has shown QFT that less emulsion is needed with E85. The main and cross channels, on the other hand, are larger to increase fuel flow to the boosters.
With the primary and secondary...
With the primary and secondary bowls and blocks already removed from our brand-new subject double-pumper, our first step was to transplant the original power valves into the new metering blocks. The power valve channel restrictions are sized at 0.076 inch, providing more "extra" fuel than the original blocks during WOT or when manifold vacuum drops below the power valve's calibrated value.