Booster Science

Booster Hop Up
Except for maybe converting a regular booster to a stepped booster, there is not much you can do to alter the basic design of a booster. That does not mean the signal gain can't be improved. Take a close look at a booster and you will see that it has a flat-face top and bottom about 25 thousandths wide. It's there because the casting process typically used to make boosters cannot produce a sharp edge. Removing a little metal from the booster's inner form as per the diagram will produce an increase in signal far beyond what you may expect from such a minor mod. It does so because the sharp edge causes more air to go through the booster rather than be deflected around the outer diameter. This mod also produces a couple of extra cfm per barrel so it is definitely a win-win move.

Another popular move is to convert the so-often-used dogleg booster to a stepped-style design. The step does little to increase the booster signal, but it does bring about better fuel shearing at the discharge point, thus causing the fuel to atomize better.

A little detailing, as shown here, can result in a 10-20 percent increase in booster signal...	...Do not remove material from the OD of the booster to produce the sharp edge because this encourages air to pass outside the booster where it will do nothing to enhance the signal...	...Here are before and after shots of this simple cleanup process.
Here is a $1,500 Nextel Cup Holley. Note the detail work to remove all casting imperfections around and into the main venturi. In addition, the dogleg boosters have had the legs streamlined and the booster's venturi edges sharpened.	By machining a step in the underside of a dogleg booster (drawing) the fuel shearing action is increased. This provides for better atomization of the fuel...	...The photo shows a non-stepped and a stepped down-leg booster. Holley offers both down-leg and annular discharge boosters with this step already machined in.