Holley have always been the uncontested number one industry leader in the fuel system technology. They have prove their selfs to be the most innovative and refreshing one out there. They produced very high quality carburetors through the years (see below for history) and are known worldwide. Holley 2 barrel carburetors and 4 barrel carburetors are very popular nowadays, we selected the best ones beneath:

The 1 barrel carburetor is the most basic form of the device. Developed in the early days of gasoline engine evolution, the carburetor replaced the vapor-wick as a more efficient way of introducing fuel into more and more powerful engines. Using the venturi effect to draw additional fuel into the airstream, the 1 barrel carburetor became standard fitment on almost all early engines.

Fuel delivery in modern automobiles has gone through amazing developments, and you won't find a 1 barrel carburetor on any new American car today. But they are used around the world in many applications. They are cheap to build, easy to adjust, and simple to operate. The only things that go wrong with them are dirt and worn throttle shafts. The third world, and much of the second, has learned to deal with these problems. The widespread use of such simple and effective devices is one reason that the first world has such difficulty in enforcing the world-wide adoption of environmental regulations.

In automotive tradition, 1 barrel carburetors were used on the smallest engines. Four and six cylinder engines wouldn't see anything more sophisticated until the late seventies. In Europe one would sometimes see the combination of two 1 barrel carburetors on a small engine in an attempt to wring more top-end power from it. 1 barrel carburetors had the advantage of not only being easy to adjust, but of rarely needing adjustment. There isn't much that can go out of adjustment.

Almost all industrial power plants, from push mowers to wood chippers, are equipped with 1 barrel carburetors. Although many power plants are based on automotive engines, they don't use the complicated controls found in cars. Some of them are primitive indeed. Briggs and Stratton used, for years, a carburetor that bolted directly to the fuel tank. The tank served the purpose of a fuel bowl and needed only to be cleaned out occasionally. The simplicity and efficiency of the 1 barrel carburetor is such that most producers of multi-cylinder motorcycles use four carburetors on a four cylinder engine. Although this introduces the additional requirement of synchronization, it provides simple and reliable power without any undue complications.

Buying a 1 barrel carburetor is usually a matter of replacing the existing one with another, identical one. If one is working with a new application, then it is helpful to find out how much power is expected. A carburetor designed for the same output can then be fitted. This is almost always the only thing that is necessary to do. Idle needs to be adjusted, and idle mixture, in the same manner as any other carburetor. Once that is done, one should have a bulletproof package that will outlast the machine it is fitted to. Don't be afraid to use a 1 barrel carburetor instead of a 2 or 4 barrel unit. When the larger carburetors are sitting on the shoulder, or in the shop, the 1 barrel will cruise right by without a hiccup.

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.

A 4 barrel carburetor is a carburetor with four venturis and four throttle butterflies. They evolved from the 2 barrel carburetor, which evolved from the 1 barrel carburetor. The history of carburetion goes back about 130 years.

When four-cycle engines were first developed, fuel was a different substance from that used today. Early engines didn't use carburetors, but a wick submerged in fuel. This was like the kerosene lamp familiar from camping trips. Air entering the engine passed the wick and absorbed fuel as vapor. This mixture was then ignited, in the cylinder, by a spark or hot wire. The expanding hot gases pushed the piston down, turning the crank and generating power. These early engines turned very slowly, and it didn't take much fuel to operate them.

As engines became larger and more powerful, they required more fuel than simple evaporation could provide. Someone, there is little evidence to support any one man as the inventor, devised the carburetor. The carburetor used the vacuum in the intake tract of the engine to draw fuel out of a bowl. Soon, carburetors became so efficient that they needed to be throttled back to keep them from running away. The invention of the throttle resulted in higher vacuum, but lower air velocity. It was soon understood that it was the velocity of the air passing through the carburetor that pulled the fuel out of the bowl. This took advantage of the venturi effect, drawing fuel into the air stream with the low pressure created by the high speed of the air.

As engines turned faster, and generated more power, the diameter of the carburetor throat increased. At a certain point it became so large that the venturi effect was reduced in strength. To keep this essential process intact, more than one carburetor was fitted. It quickly became obvious that a carburetor with two venturis was cheaper to produce than two separate carburetors, and the two barrel carburetor was born.

The 4 barrel carburetor is actually a pair of 2 barrel carburetors joined together in one piece. The primary barrels act as a 2 barrel carburetor during cruise and slow running. When more power is needed than the primaries are capable of producing, the secondaries open. These additional barrels are opened either mechanically or by engine vacuum. The vacuum method works better with automatic transmissions, as it is more easily adjusted.

4 barrel carburetors, while capable of making more power than a 2 barrel carburetor, will generally return higher gas mileage. This is because the smaller primary venturis operate more efficiently in the cruise mode. If one goes about with the pedal against the floorboard, mileage will suffer. This makes the 4 barrel carburetor the best choice for a replacement or new application on any engine that will accommodate it. 4 barrel carburetors are also generally less expensive. Tuning and adjustment of them has become widely known, and getting a new one going rarely takes more than an hour or two.