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Most carbs with accelerator pumps will provide fuel to the accelerator pump until there is nothing left in the float bowl. The idle circuit will also pull fuel until the bowl is empty.
The main circuit relies on the fuel level in the float chamber to operate properly.
The previous statement about float bowl fuel level changing is not correct. the fuel level remains very constant in the float bowl, probably within 1 millimeter since the float level controls the activation of the needle valve that refills the float chamber. That is a very precise control mechanism and it needs to be for the main jet to consistently supply a precise mixture.
You can argue the precision of the mixture all you want, but consider this, fuel economy did not change much when delivery transitioned to fuel injection and Honda's CVCC designs are still top dogs in economy and in their time period were good enough to delay the adoption of catalytic converters.
Precision measurement of the actual amount of fuel in the float chamber, followed by letting the engine idle with the fuel pump shut off will give you a very good idea of the idle consumption, which in most V8s is about .5 gph.
Once you have converted that consumption into a time period that the engine will idle on the fuel in the float chamber and you know the volume of the chamber, you will have that time recorded and can calculate other scenarios using time (to empty float chamber) to calculate the consumption based on the idle consumption time. Half the time twice the fuel and any point above or below the idle consumption time period can be easily calculated as a fraction of X/idle fuel consumption time.
regards
mech
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