That is what has me confused. I ran my hoodless '27 for years with a very overcarbed 302 Ford (two fours) and a very chopped windshield, and got none of the symptoms you are describing. Exhaust fumes would do what you describe.

Do you have open headers exiting in front of the cockpit or a full exhaust system? Something is putting out exhaust fumes, like leaky header gaskets, etc. I can't see a rich carb doing this because the unspent gas would exit through the exhaust system.

Something is missing from this scenario.

Don