The 2 barrel carburetor is generally a simple device, although we'll see later that this is not always the case. Carburetors were developed right along with the four-cycle engine. As the composition of fuels changed and improved, carburetors did the same.
Early engines turned slowly, sometimes not exceeding the idle speed of a modern engine. This meant that the air in the intake tract moved slowly. In the beginning, a wick was used to evaporate fuel into the air entering the engine. This resembled a camping lantern in operation. Engines became more powerful, though, and a way was found to admit larger quantities of fuel into the engine. Early racing practices accounted for many of these improvements. The carburetor, soon coming into wide use, took advantage of the venturi effect to dispense fuel. Simply put, the faster the air passes through the carburetor, the lower the pressure in the throat of the carburetor becomes. By placing a fuel-dispensing hole in the carburetor throat, greater quantities of fuel could be mixed with the air and admitted to the engine.
There is a practical upper limit to the size of an effective venturi. When engines were developed to the point where they needed more fuel than a simple carburetor could provide, the manufacturer simply fitted two carburetors. This worked, but introduced extra costs into the car. While this was not a problem in a Duesenberg or Packard, Ford and Chevrolet were in a cut-throat battle over prices. So, the 2 barrel carburetor was invented. It packaged the power delivery of two carburetors into the space of one, and only cost a bit more to build. The manufacturers of big and powerful cars didn't suffer, they could now fit two 2 barrel carburetors to their engines for even more power.
In America, the standard carburetor fitted to a V8 engine became the 2 barrel. 4 barrel carburetors were considered to be a luxury or performance item. This was an artificial distinction brought about by the advertising and marketing men, abetted by the insurance companies. Owners of 4 barrel carburetors were forced to pay extra for insurance, and for their cars.
In Europe, the 2 barrel carburetor also became popular for other reasons. The small engines of European cars did not produce a lot of power, but they operated over a wider range of engine speeds. The small carburetor needed to idle and cruise was not sufficient for full-power operation. So, they developed a 2 barrel carburetor with two separate throttle shafts. One operated as a primary throttle, and the other opened when more power was needed. Like an American 4 barrel carburetor, this system worked well, and was adapted in the U.S. when small engines began to be used. These carburetors are still an excellent choice for small engines. There are many racing classes in the U.S. which require the use of 2 barrel carburetors. This is done to level out the competition and keep costs down for the participants.
