How to Build an Alcohol Engine

by Allison Boyer

Gas prices are perpetually on the rise, leaving today's leaders in the automotive industry searching for green solutions. You don't have to purchase an expensive hybrid or wait for the electric car, though. With the right tools, you can build an alcohol engine in your existing vehicle, and since most of today's cars, trucks and SUVs are already built using ethanol-compatible parts, the process is also relatively inexpensive for most people.

Step 1

Test your parts to ensure they can work with alcohol-based fuel. Clean your fuel pump, carburetor, fuel filter and fuel hose, and soak them in at least 180-proof alcohol for about a month. You'll need to replace anything that shows softening or other damage due to the alcohol.

Step 2

Remove and disassemble the carburetor. You'll need a carburetor overhaul kit specifically made for your model carburetor to modify it for use with alcohol.

Step 3

Enlarge the fuel-metering jets of the carburetor carefully using a drill press or hand drill. Typically, you want to increase the size by about 40 percent, but this varies depending on the purity of the alcohol you use.

Step 4

Adjust the float setting or purchase a heavier float. Alcohol is up to 8 percent heavier than gasoline, so you need to bend the float up slightly or use a new float to maintain the proper fuel level.

Step 5

Reassemble the carburetor and fit it back into the engine. You should be able to connect it just as it came out, with no extra or leftover parts.

Step 6

Advance the timing of the ignition system, since alcohol burns at a higher rate and takes more time to ignite and vaporize. To do this, loosen the distributor by turning it in the direction opposite of the turning rotor inside.

Test drive your car. Engines vary from vehicle to vehicle, and you'll likely need to make some adjustments to prevent the engine from cutting out or to stop pinging due to poor timing.


  • You'll need a small amount of gasoline to start the engine in a cold environment, as alcohol won't start at temperatures lower than 60 degrees F. If you don't have a timing light, you can time the ignition manually. Start by advancing the timing just 1/16th of a turn. Test drive the car, and keep advancing it until you don't hear a pinging noise anymore. The correct setting is just below that point. You may get better results by using spark plugs rated for ranges hotter than the spark plugs you are currently using; the higher the ranges, the "hotter" the plug. Be careful not to use plugs that are too hot by checking your engine for white or blistering electrodes. If you're worried about making a mistake, try converting an older engine first as a test run. Keep in mind, however, that worn parts make it harder to get the settings correct. Visit your local scrap yard if you can't keep your engine apart for a month to test the parts in alcohol. Ask for unusable engine parts that are the same as the ones you'll be using and test those instead. Often, since they are unusable otherwise, they'll give them to you for free.


  • Never drill the jets before removing them from the carburetor, as shavings could fall into it and create engine problems. To make, buy or store alcohol for fuel, you need to obtain the proper licenses from the state or you could face fines and other legal problems.

Items you will need

  • Mechanic tools
  • Working gasoline engine
  • 180+ proof alcohol
  • Carburetor overhaul kit
  • Drill press or hand drill
  • Heavier float
  • Hotter spark plugs

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