Hot Idle Compensation valve front side

I am NOT Suggesting this is the correct part number!!! Just an illustration of the front side of the valve!!! Here is an example of the Hot Idle Thermal Unit that fits in the casting in the rear of the Carb. Under the bimetal strip is a cork disc that is used as the seal. You probably threw away the cork disc when you did the carb overhaul because you did not need it. (Probably wondered what it was for) Many GM Applications used this in their carb.   The Cover holds it in place.  Remember: I'm simply showing that GM has had to deal with Hot fuel and Hot Conditions in many applications

Many vehicles had some form of hot idle compensation. During hot conditions far too much fuel is vaporized in the float bowl and being ingested by the engine. The Hot Idle Compensator increased the amount of air flowing under hot conditions. With fuels used today Hot Idle compensation may be needed.