The problem you describe can be caused by many factors, not necesarily the carbs but that does sound favorite, You do not know the choke size, this should be 30mm if the rest of the engine is standard, The bigest thing that will affect the running is that you are trying to get more fuel mixture into the motor by running the webers, but what goes in has to come out and the best thing you can do is to get a good set of headers and also a head job! not increasing the valve size but matching the port size If you do not do this you will never get the advantage of the larger carbs, It is well worth the effort and then you can think about the jet size but what you have providing the choke size is not to large sounds about right, Did you check that all the jets match! as quite often the size stamped on them does not match the hole size due to many years of experts!!! messing with them, Stick with them and providing the rest of your motor is sound you will not regret it.

I did not check the jet sizes with a gage, but the numbers all match. I bought the car as is. Personally, I wouldn't have put the webers on unless I was going to also add a higher performance cam. Can't afford cam setup, so must try to get these carbs working as well as possible with the present equipment. The engine has only 2 hours running time on rebuild, including head job. Not really broken in yet. Thanks, victor.