Over sized needle and seat, metal floats and big jets. Just set it up like an alchy carb and jet appropriatly. you won't need as large a jet as a true alchy carb because of the gasoline in the mix.
Better check to see if the zinc casting on an old carb is compatible with E85. I'm not sure, but better do the homework than have a trashed casting in a few months.
Not recommended for longevity. E85 is extremely corrosive - it'll tear up the casting as well as any non-compatible lines and pump components.
Check out the Historical Vehicle Association. They have several "tech" articles on ethanol. It is nasty stuff and will eat up the old carbs and component parts.
Don't use rubber. Alcohol eats rubber. You'll need to change any cross-over tube pieces or other rubber pieces too. Also any rubber hoses in the system. It'll soften a lot of plastics too... Mike
You guys need to get your chemistry straight. Ethanol is not corrosive. Ethanol is a solvent. This means that it dissolves things (natural rubber for one). The corrosive aspect comes from the water and metals that are often held in solution with the alcohol. Ethanol has a hydroxyl molecule (-OH) that it readily gives up to bond with other molecules. The hydroxyl reacts with the water and trace alkaline metals (sodium, magnesium, zinc, etc) to form a weak acid that can be corrosive if the conditions are right. Ethanol is just like gasoline in the sense that you need to Keep the Water OUT. The oxygen that ethanol carries with it is what makes it a good fuel choice. Just like nitromethane, you can cram more fuel into a cylinder and need less air to make it go bang. You also can run much higher compression ratios with ethanol. Nothing is more important to the overall power and efficiency of a piston engine more then compression ratio. That is why 8,000+ lb 1-ton diesel pickups will pull 20+ mpg on the highway - Very high compression ratio. Ethanol gets a bad rap because people are trying to run it in engines designed for gasoline. That makes about as much sense as running diesel in a gas motor. Design and build an engine for ethanol and it will run circles around a similar gasoline motor.
In the 1930's, zinc alloy carburetor bodies to be used with alcohol (yes, Virginia, they did have alcohol in the 1930's) were nickel-plated to protect against the alcohol. Electroplating is NOT my field. I have been told by some old-time platers that once there was a nickel-plating process that could be done at low heat (less than 350 degrees F.), but that process was banned by the EPA. Modern nickel-plating uses a process that requires more heat, and will cause "slumping" of the zinc alloy metal. As mentioned above: Leather accelerator pump Oversize jets and discharge nozzles Alcohol resistant gaskets (we use Armstrong N-8090) Oversize orifice in the fuel valve(s) seat(s) Brass floats Monel steel fuel valves I would flush the E-85 after each race, and expect to replace the entire carburetor after each racing season (perhaps more often). If the nickel-plating could somehow be accomplished, the longevity would be significantly increased. Jon.
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