There's no end to the theories regarding carburetion, performance, and fuel efficiency. Just about everyone has a belief they stand by when it comes to carburetors. Fatten the mixture. Lean the mixture. Use this jet. Use that jet. Swap the power valve. Change the boosters. Use this gasket. Use that gasket. Raise the float level. Lower the float level. Use vacuum secondaries. Use mechanical secondaries. Eliminate the power valve. Use an open-element air cleaner. Maybe a more aggressive accelerator pump cam. And choose a carburetor: Holley, Edelbrock, Carter, Stromberg, Weber, Barry Grant, Autolite, or Motorcraft.
Everyone has an angle for carburetor selection and tuning. Our job is to help you make informed decisions when it comes to your carbureted fuel system.
How Do Carburetors Work?
The carburetor was invented in 1893 by Dont Bnki, a Hungarian engineer. It was a pivotal point in the development of the internal combustion engine because it revolutionized the fuel/air management process. The carburetor's function is rooted in the Bernoulli principle that air flow through the throttle bore dictates how much fuel and air enter the combustion chambers. When we open the throttle, air flow increases through the throttle bore which draws on the fuel in the fuel bowl.
In over 100 years, carburetor basics haven't changed much, and the principle remains the same as in 1893 when the carburetor was invented. It is all about air flow, speed through the bores, and how each draws fuel from the fuel bowl. This is a Holley 4160 carburetor provided by MCE Engines of Los Angeles. | 
There has to be enough fuel in the fuel bowl to keep the engine supplied. The float and needle valve control how much fuel enters the carburetor. As the float falls with the consumption of fuel, it relieves pressure on the needle valve, allowing more fuel into the bowl. The float rises against the needle valve, closing off the flow of fuel to the bowl. In normal operation, float movement isn't even perceptible. It maintains a smooth flow of fuel into the bowl. |
This is a center-pivot Holley fuel bowl with a brass float. Brass floats are sometimes recommended because foam floats can take on fuel, sink, and stop doing their jobs. Brass floats can also leak when a solder seam gives out and the float fills with fuel. Each type has its advantages, and every carb tuner has a preference. | |
No matter how large or small, the carburetor's job is to mix air and fuel in the proper proportions to support combustion in an internal-combustion engine's chambers. How much power an engine makes is directly proportional to how the carburetor mixes the fuel and air. But the carburetor's job is only the beginning of the power process. Everything has to work together in order to yield precise fuel/air delivery. The proper combination of carburetor, intake manifold, cylinder heads, camshaft/valvetrain system, and exhaust scavenging is necessary to make the most of an engine's potential for power.
To understand how carburetors work, we have to examine each of its systems; floats, accelerator pump, idle/low-speed circuit, cruise/power circuit, and throttle bores/plates.