Holley Model 2280 Carburetor

Fig. 1 1983-86 Holley 2280 two barrel carburetor:

This carburetor, Fig. 1, uses four basic metering systems. The basic idle system provides the proper air/fuel mixture for idle and low speed operations. The accelerator pump system provides additional fuel during acceleration. The main metering system provides the proper air/fuel mixture during normal cruising conditions. The power enrichment system, combining a mechanical and vacuum operated power valve, provides a richer mixture when higher engine power is required.
In addition to the four basic systems, there is a fuel inlet system which supplies fuel to the four basic systems and a choke system which temporarily enriches the mixture to aid in starting and running a cold engine.