A reasonable definition of a street rod is a vintage car modernized with improved performance for today's roads and travel speeds. Of course if you're reading this you already knew that, but while installing modern suspension, brakes, and updated motors was once all it took, today you must also deal with the ever-changing landscape called technology. One such challenge is how and if "modern" E10 gasoline is affecting your vintage carbureted hot rod.

We say modern, but actually ethanol pre-dates the automobile and has been around since the Civil War. Many hot rodders are unaware that the Ford Model T was originally designed to run on ethanol or gasoline. Henry Ford was a huge advocate of bio-fuels with a vision of converting crop waste to alcohol to fuel his factories and the cars he built. Through a series of twists, turns, legislation, and power brokers, alcohol has come and gone several times over the past 100 years, but it now appears E10 is here to stay.

There are two serious concerns with ethanol blends: too-high RVP (Reid Vapor Pressure) causing vapor lock behavior and percolation of the fuel. The second problem arises when fuel sits for a period of time, the technical name is water-induced phase separation. For automotive use, vaporlock concerns vanished with modern electronic fuel injection. The E10 gasoline was designed for and works perfectly well in a modern car with fuel injection and the associated fuel pump and return line. Since the fuel circulates continuously, it never gets hot enough to vaporize, and thus never vaporlocks. Even if there were vapor in this system, with the fuel flowing in a loop it would simply be pushed through the line, much like bleeding brakes.

The problems begin with a vintage fuel system that employs a dead-head pump and float bowls where the fuel can heat up and percolate. This problem is particularly acute after running the engine for a sustained period of time at highway speeds, then suddenly coming into stop-and-go traffic. The associated heat sink effect will elevate the temperature of the carburetor and the fuel will boil in the bowl. This can lead to serious flooding on some cars and hard starting problems when hot in other vehicles, while many other cars may notice rough idle characteristics.

Not being a pure substance, gasoline has no single boiling point. Instead, the lighter fractions start boiling out at 90-100 degrees F, with more and more evaporated as the liquid temperature increases, until the final, heaviest fractions evaporate in the 300-400 degrees F range. This behavior is called the "distillation curve." Ethanol boils at 178.5 degrees F, while water boils at 212 degrees F. The trick in a carburetor is to make the fuel evaporate into fumes when atomized without lowering the boiling point.

To prevent the fuel from boiling in the carburetor or fuel lines you should insulate the carburetor base to prevent unwanted heat sink. A heat shield will also help to reflect radiant heat away from the carburetor bowls, while insulating fuel lines will help prevent pre-heating the fuel. If there is no heat shield available for your carburetor you can either fabricate one yourself or you might try putting some of the hi-tech heat reflective tapes directly on the bottom of the fuel bowl of the carburetor. It will also pay to insulate incoming fuel lines and exhaust pipes that exit under the gas tank or close to fuel lines.

The second potential problem is also not likely to affect new cars. Water-induced phase separation is caused by alcohol's natural tendency to absorb moisture. If you fill and consume the fuel in your tank on a regular basis this problem is rare as the fuel does not have time to absorb substantial water. However, most street rods sit for more days than they are driven, and all the while they are sitting in the garage the alcohol is busy absorbing water from the air. At some point the water separates from the alcohol and your street rod is now running unintentional and intermittent water injection; this is not a good thing. These pockets of water cause misfires when running, but worse yet that water and alcohol has become a corrosive agent that is busy eating your pot metal carburetor and rusting that steel fuel tank. Storing the car with a full tank helps reduce the amount of air in the tank and you should also introduce a fuel additive to stabilize the fuel.

Ethanol reduces emissions, and that my friend is a good thing. On a down note ethanol also attacks unprotected aluminum and pot metal. Yes, that means your carburetor is under attack. Ethanol has been used in varying amounts since the 1970s as an octane enhancer, but it wasn't until the '90s that the levels were elevated to the 10 percent ratio of E10 gasoline.

Here are some materials that cannot be used with ethanol but can be used with pure gasoline. Do not use old-time lacquered cork carburetor floats, the antique zinc-based "pot metal" castings for fuel pumps and carburetors, and Lexan or Plexiglas if there is warm vapor contact with ethanol fuels. Of course you can change the floats and hoses but that carburetor is pot metal so it will require some protection; we'll get to that shortly.


1. Ethanol can be highly corrosive, and one look inside this carburetor tells us something in the fuel system is rusting—most likely the steel tank itself. Fine rust sediment has lined the bottom of the carburetor bowls.

2. Oxidation and phase separation of the fuel itself will lead to this type of deposit, which of course leads to poor performance and possible flooding if sediment becomes lodged between the needle and seat inside the carburetor. Even with a good filter the untreated fuel can produce sludge in the carburetor.

3. AMSOIL INC. Quickshot is a premium fuel additive formulated to thoroughly clean and restore peak performance in automotive and small-engine fuel systems. It also stabilizes fuel between uses and during short-term storage. Its revolutionary technology focuses on three major fuel-related issues plaguing these applications: Ethanol, water, and dirty pump gas. When an ethanol/water mixture is pulled into the engine, it creates a lean burn situation that increases combustion chamber temperatures and can lead to engine damage. AMSOIL INC. Quickshot is designed to keep water dispersed throughout the fuel tank, moving it out as a normal part of operation and decreasing the chance of ethanol separating from the gasoline. AMSOIL INC. Quickshot was tested in fuel containing 10 percent ethanol. Controlled plugging of injectors showed a 70 percent flow improvement, while oxidation stability improved 44 percent over untreated fuel.

4. Driven’s Carb Defender Fuel Additive is specifically formulated to protect against ethanol corrosion and induction deposits. Special corrosion inhibitors work to prevent expensive repairs and diminished performance caused by ethanol-blended pump gasoline and the moisture it attracts. High levels of ethanol dilution in motor oil can lead to rust and other corrosion problems in the fuel system and inside the engine. This new additive, however, controls combustion chamber residue, plus cleans and protects surfaces of the fuel system and intake tract. The additive treats up to 25 gallons of ethanol-blended gas, and should be used with each and every fill-up. Driven Racing Oil Carb Defender Fuel Additive keeps the carburetor functioning properly and is designed for the unique needs of classic vehicles that spend much of their lives in storage between cruises and special events.

5. Eastwood’s Fuel Guard additive prevents the harmful effects caused by ethanol and prevents corrosion, gumming, and resin buildup. Use Fuel Guard Protection formula with every fill-up and Fuel Stabilizer formula for storage up to 12 months to prevent ethanol phase separation and corrosion. Fuel Guard also keeps carburetors and injectors clean and the formula contains no harmful alcohol or hydroscopic additives.