Changing pump cams is done by removing one screw, placing the new pump cam next to the throttle lever, and tightening it up. There are two and sometimes three holes in each pump cam, numbered 1, 2, and 3. Placing the screw in position No.1 activates the accelerator pump early, allowing full use of the pump's capacity. Generally this position is best for vehicles that have lower idle speeds (600 or 700 rpm) because there is a good pump shot available as the engine comes off this relatively low idle. Positions 2 and 3 delay the pump action, relatively speaking. These two cam positions are good for engines that idle around 1,000 rpm and above. Repositioning the cam makes allowance for the extra throttle rotation required to maintain the relatively higher idle setting. Pump arm adjustment and clearance should be checked and verified each and every time the pump cam and/or pump cam-position is changed. CT
To prevent the power valves from being blown out, Demon carburetors have a check valve in the baseplate. | 
Accelerator pump squirters come in an assortment of orifice sizes. Larger orifices require a special screw to allow a larger volume of fuel to pass. | 
The fuel system's best ally is a good filter. The BG 5000 is light, compact, and its replaceable element filters to 8 microns. They can be used with gasoline, alcohol, or nitro. |
The mertering block directs fuel to hte passes in the carburetor's main body. | | |
1.
Idle circuit fuel enters here from a main jet. The vacuum below the closed throttle plates at the idle discharge orifices and transfer slots draws the fuel upwards through internal idle circuits to the idle feed restrictors. The idle feed restrictors regulate the amount of fuel in the idle circuits.
2.
At the idle feed restrictors, the fuel is introduced to the air that is traveling down from the idle air bleeds above (also drawn by the vacuum below the closed throttle plates). Emulsification (mixing) of air and fuel occurs in this vertical channel as the air/fuel mixture for the idle circuit travels downwards to the idle discharge orifices and the transfer slots, located in the baseplate.
3.
Passageway that leads to a transfer slot. The function of the transfer slots is to provide sufficient air/fuel mixture during the transition between the supply of idle circuit fuel and main circuit fuel.
4.
Passageway that leads to an idle discharge orifice. The function of the idle discharge orifices is, unsurprisingly, to provide sufficient air/fuel mixture during idle. Adjustment of the idle mixture is performed by the adjacent screws, which penetrate these particular passageways.
5.
Power valve aperture. Usually, power valves are considered unnecessary in drag racing applications. They are more suited to cruising and generally work in conjunction with smaller main jets, providing additional fuel when required.
6.
Emulsion bleeds are set in the main fuel circuits. Air is drawn in from the high-speed air bleeds above and mixes with the fuel in adjacent internal passageways behind the emulsion bleeds. The vacuum generated by the boost venturis draws the emulsifying main circuit fuel upward, out through the main well exits at the top of the metering blocks (No. 7), and discharges it through the boosters.