Carburetor Air Bells & Intake Velocity Stacks

By smoothing airflow from incoming air, velocity stacks maximize the amount of air that can enter an engine. Combined with additional fuel, when ignited, higher combustion will occur, resulting in more horsepower and increased engine performance.

By changing the velocity stack to a different length, you can tune your engine to maximize power in a specific RPM range. Shorter lengths give you more power at higher RPM while longer lengths improve low RPM power.

A velocity stack is a cylindrical tube with an inlet opening that is shaped similar to a trumpet horn. It attaches to the beginning of the carburetor air inlet. The velocity stack intake design smooths incoming air, which allows more air to be able to enter the engine, resulting in increased horsepower. Installing a velocity stack is a simple DIY project, usually attaching to the carburetor air filter stud.

In general, velocity stacks, correctly matched to a specific engine combo, yield about 3% increase in power. That equates to roughly 10-15 horsepower on a 400 horsepower engine. If the wrong velocity stack is used however, the opposite can happen and your engine can actually decrease in horsepower.

A velocity stack air filter is an air filter that is designed either as a part of the velocity stack or to fit at the top of the velocity stack. The filter screen prevents dust, dirt, and other debris from entering the engine.

Some velocity stacks use air filters while others do not. For street use, a velocity stack with an air filter is highly recommended to protect the engine from damaging debris that could enter the engine from varying road conditions. For drag racing, velocity stacks are often used without air filters to further increase airflow and power. With limited engine use, the risk of dirt entering the engine through the carburetor (Holley Dominator for example) is reduced a lot more than driving for miles on the street.