How to Convert a Carburetor to Ethanol

by Keith Allen

Ethanol, a form of alcohol, is a renewable fuel, produced from plant materials that can be grown each year. Ethanol is not interchangeable with gasoline. Vehicles intended to run on ethanol will require several modifications to the fuel delivery system including the carburetor. These changes are necessitated by the lower energy content of ethanol and its corrosive properties. These modifications can be accomplished by a competent amateur mechanic. Commercially available kits can make the process easier.

Carburetor Conversion

Acquire a spare carburetor. Converting a second carburetor to ethanol has a couple advantages. It keeps the vehicle in service while the work is being done and gives the car owner the ability to revert back to gasoline, by re-installing the original carburetor, if necessary. Check salvage yards for a used carburetor.

Install a carburetor kit. Carburetor kits are prepackaged parts kits containing valves, gaskets and any other parts particular to that carburetor model that can wear or deteriorate. Installing a carburetor kit overhauls the carburetor.

Find and measure the jets, the openings where fuel is forced under pressure into the mixing chamber. Because ethanol contains less energy than gasoline the amount of the fuel introduced to the engine must be increased. Measure the opening, which will be small, very accurately. Use a micrometer, if available, or take the jets to a machine shop for measurement.

Increase the size of the jets by 40 percent. Calculate the new size based on the measurements of the original jets. Determine the proper size of drill bit and use it to enlarge the jet. Home mechanics without access to a full set of drill bits and a drill press can have this work done at a machine shop. Another option is to purchase new jets of the appropriate size, if available, from an auto parts retailer.

Alter the carburetor float. Ethanol is denser than gasoline which would result in the float riding too high and stopping the flow of fuel into the carburetor. The float arm can be bent but that is a trial and error process and can be difficult to accomplish accurately. Another option is to add 10 percent to the weight of the float. Remove the float and weigh it. Calculate 10 percent of the float's weight and solder an equivalent lead weight to the float.


  • Make note of the fuel lines and control linkages of the gasoline carburetor before removing it from the vehicle. Make sure the modified carburetor is properly installed before attempting to start the vehicle.

Items you will need

About the Author

Keith Allen, a 1979 graduate of Valley City State College, has worked at a variety of jobs including computer operator, medical clinic manager, radio talk show host and potato sorter. For over five years he has worked as a newspaper reporter and historic researcher. His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines.

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