As downunder told everyone, without the muffler pressure the Carbs on modern engines are far too overbored to draw fuel. That venturi has to significantly increase dynamic pressure so there is less static pressure for fuel to flow. Bore it out and you get no fuel flow, simply because the increased area doesn't require adequate airflow velocity to significantly increase dynamic pressure with the resulting decrease in static pressure, that really sucks the fuel. I make carb restrictors for sport engines for club friends so they get more steady and reliable engine runs.
Pull the muffler pressure line and go up without changing the needle valve. See what happens.

Back in the unmuffled days, the carb throats were much smaller than today for a given engine size. They ran more reliably, yet not nearly as strong.

Go fly your Dubb Jet with a carb hole that can swallow a bird. You have to really under prop it so as to obtain the RPM required to feed that monstrous hole. Otherwise expect flameout right after T.O.

Of course there are true pressure tanks, but then the idle really suffers. If you want the best of all worlds, Try one of Dubb Jett's BLADDER tanks. Very neat, but alas, you gotta' have muffler pressure! [sm=52_52.gif]

If you just have to have the ultimate power, then simply increase cubic inches.