mercedes 220s carburetor problem

[jof]

Hi petrol heads . We have a 220s ponton with the one carburetor version . It appears to be a twin carb one side feeding the front of the engine and the other the rear .
The problem is the fuel is not vaporizing out of the main jets ,it appears to be dripping out and lumpy .
The emulsion tubes were open at the bottom and there was no sign of the plastic sealing balls I have read about in this forum so I have sealed the ends with solder but this made no difference .
The engine has had a rebuild ,cylinder compression is even , I went around the carb and manifold with carb cleaner and no sign of a leak and there is good suction at the carb .
Any help or clues would be greatly appreciated . The car starts and runs fine although there is a huge dead spot and after about 25 miles the plugs soot up and it starts to pop and miss fire . It also ticks over beautifully.
thanks jon