I might have a line on this issue. Insulated the front half of the manifold, under the fuel bowl with exhaust packing. It helped. Slowed the temperature increase in the bowl from 10 minutes to about 30 minutes.....less perking and less fuel leaking over all but still not fixed.
Here is the max temp reached in the bowl, hood down, 30 minutes post shutdown....ambient air temp is 65ish degrees.
Got a wild hair a few minutes later and opened the hood and read the temperature of the adapter manifold interface....read at the adapter, above the 1/4 thick gasket....
Now this is with the hood open and things are cooling rapidly....
Immediately read the temperature of the outside of the bowl, midway up the side of the bowl....the side, most exposed to the cooling air.
Then read the temperature of the carb top, between the carb top cover and the air cleaner adapter.....the hood has been open now about 10 minutes after reading the max temp of the fuel in the bowl (hood closed for those readings)
Methinks this may be lots less about radiated heat from the manifold and bunches more about a lovely aluminum adapter transferring heat right straight up from the manifold and into the carb. At idle and immediately after a run the bowl is cool to the touch and often has a bit of condensation on it....not perkin or boilin till after it shuts down/air flow into the carb is stopped.
Betcha I need a phenolic insulator between the carb and the adapter.