<VV> Smokin' carb

[Grant Young]

This could be any one of a myriad of things. These are some things I have run in to over the past couple of decades. I'm sure you have checked most of them, so this is just in case note...:
-The first thing to check would be is the operation of the chokes. Are they opening all the way and on time? Do they hold a vacuum?
-The next would be to determine if the float assist springs were installed correctly. They will hold the floats open, if not.
-Linkage adjustment could also be a contributor if carb is not closing fully, so check them without as noted in another post.
-If the throttle shafts were replaced, make sure the throttle plates are installed correctly. They can be inserted backwards, but won't work. Are they covering the ported vacuum slots when closed? 
-Are the base vent springs working correctly. You can disable them without much effect if you think they might not be. 
-Are you sure you installed and tightened both jets.
-Did the power enrichment needles come out and go in easily. If they stick open it is like having a jet size of .080" or more.
-If the throttle shafts were not replaced, they are most likely the problem. They can "look okay" and be "in spec" on the bench, but the carb or shaft can be worn enough so that the linkage will pull it out of spec (open too far) under load. O-rings won't fix the problem.
-Carb tops can warp if tightened too tightly and leak around the bowl cover gasket. About the only way to tell is to lay a straight edge across the inverted (no gasket) top to see is there is clearance more than the thickness of the gasket. (hard to repair, BTW).
- If the idle speed screw is turned in too far when adjusting, it will cause the ported vacuum slot to be exposed to the engine when it shouldn't be and the carb will try to operate in the power circuit and cause too much fuel to flow (drip) into the venturi and puddle and dump into the head (causing smokin'). Since it runs okay for a minute, you might move this to the top of the list.
- If all else seems okay, I think I would suspect a valve adjustment issue, unless the problem just started with the rebuilt carbs. I have seen engines backfire or smoke through the carbs due to a broken valve springs. 
Hope this helps, (I'll look at them for the cost of postage, if you want).
Grant
 

Question re symptoms: Is a "smoking" carb a symtom of something? 1965 110 PG runs OK for about a minute, then bucks like it will stall but"recovers" running rough. After shutting off (with key), both carbs "smoke" Putting hand over left carb gives me a palm full of gas. Putting hand over right carb doesn't.
Vacuum hoses and fuel lines are all new.Both carbs are rebuilt as close to Bob Helt's specs as possible, and all ports pass carb cleaner freely, floats balanced and compression  is 140-150
in all cylinders.