DIY





Our Gasoline and Alcohol-Powered Dual-Fuel Van

The latest project in our ongoing ethanol research program resulted in the successful conversion of a Chevy van to gasoline and alcohol dual fuel capability.

| January/February 1981

Well over a year ago, this publication detailed an alcohol fuel conversion performed on an experimental six-cylinder Chevrolet pickup truck. Since that time—in the true spirit of research—MOTHER EARTH NEWS has continued her firsthand investigation into both the production and use of the renewable liquid energy form.

Our latest alternative-fueled vehicle is a 1977 Chevy 1/2-ton van equipped with a 250-cubic-inch "six," an automatic transmission, and a "flip-of-the-switch" genuinely efficient dual-fuel system! The modest hauler has racked up over 12,000 trouble-free miles in its gasoline/alcohol configuration, and it serves MOTHER EARTH NEWS' traveling seminar crew as both a workhorse and an eye-opening educational tool ... while also providing an excellent test bed for other automotive research.

Double-Barreled and Drivable

As you might imagine, our twin-fuel system is based upon two carburetors. The van's original Rochester downdraft model was replaced with a pair of sidedraft Carter YH's (an older automotive carb that's now widely used in marine applications) mounted on a homebuilt "Siamese" Y manifold that was fabricated from muffler tubing and flanges. The front "fuel mixer" is relatively unchanged and runs on gasoline, while the rear atomizer has been modified to suit the requirements of ethanol. Both mechanisms are individually controlled by a solenoid-operated selective sliding throttle linkage made from some flat stock and—believe it or not—a 4" door hinge.

Rather than heat the alcohol fuel, as we did on our first test truck, we chose to preheat the air entering the ethanol carburetor (from ambient temperature to 170°F) in order to improve vaporization. We also took advantage of the liquid's high "octane" rating by automatically advancing the timing when burning alcohol, while carefully controlling spark "progression" in the gasoline mode to guarantee "knock-free" performance.



The "Boring" Details

As you might imagine, the latest conversion was a good deal more involved than was that of our original Chevy six, and for two good reasons. Primarily, our goal was to improve both fuel economy and vehicle drivability beyond what we'd achieved in the initial conversion (although both were certainly acceptable for an admittedly experimental vehicle). Consequently, we chose to use the horizontal-style carburetors not only because they offered the convenience of dual-fuel capability, but also because their sidedraft design afforded the least restrictive fuel flow from the float bowl to the "booster" venturi area within the mechanism's throat ... though some of the internal passageways still did need modification. (Conventional downdraft carbs would require reworking, too, but might not perform as well because of their "serpentine" fuel-feed galleries.)

So—armed with flat and needle-nosed pliers, a screwdriver, a wire gauge set, and a complete assortment of drill bits (numbered sizes 1 to 80, plus one 19/64" version)—MOTHER EARTH NEWS' car doctors prepared to perform surgery on the alcohol-carburetor-to-be, after first dismantling the unit and cleaning it thoroughly with solvent. (This preparatory operation included the removal of the press-fit plugs that sealed the factory-drilled fuel passageways from the outside.)






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