Looks to me like you are missing everything that actually makes up the hot idle compensator.
From the Delco Carburetor Models 2G, 2GC, 2GV Service Manual 9D-3 MAY, 1973 Supersedes 9D-3 dated Aug., 1964 the following description of operation of the hot idle compensator and parts are as follows:
During prolonged idling in heavy traffic in hot weather, under-hood temperatures can exceed 200 degrees Farenheit causing severe percolation or boiling of fuel in the carburetor float bowl. With excessive heat, all fuel vapors cannot be eliminated through normal venting and some will be drawn into the carburetor bore and intake
manifold resulting in over-rich idle mixtures. The rich mixture causes a rough idle and may even cause engine stalling.
The Hot Idle Compensator is used on some 2G carburetor models to off-set the enriching effects caused by these excessive fuel vapors by supplying additional air to the intake manifold when idle air/fuel mixtures become rich due to temperature increase The compensator consists of a thermostaticallycontrolled valve usually mounted in the area above the main venturi or at the rear of the float bowl. The valve closes off an air channel which leads from above the carburetor venturi to a point
below the throttle valves.
The compensator valve is operated by a bi-metal strip that senses temperature. At a certain predetermined temperature, when extra air is needed to off-set the enriching effects of fuel vapors, the bi-metal strips bends and unseats a valve which uncovers the air channel leading from the carburetor venturi to below the throttle valves.
At this time, just enough air is added to the engine to offset the richer mixtures and maintain a smooth engine idle. When the engine cools and the extra air is not needed, the bi-metal strip closes the valve and operation returns to normal mixtures. Hot idle compensators are pre-set at the factory and require no adjustment.
However, to insure proper idle adjustment, the valve must be closed when setting engine idle speed and mixtures. This can be done by using a screwdriver to press down lightly on the valve for those models with the valve located in the main venturi area (left picture). On those models with the valve located at the rear of the float bowl (right picture), hold spring-loaded button "in" when making the idle settings. If no button is available, remove idle compensator cover and using a screwdriver, press
in lightly on the valve when making idle settings. Replace cover after completing idle adjustments.
