I have also spent a lot of time trying to cure the cold flat spot and spitting back throught the carbs. My car is a 1700 crossflow with twin 40s, 234 cam, ported head with 41.3/34.9 (1.625"/1.375") valves. Current jetting is: (original jetting in brackets) Main venturi 36 (32) Main jet 130 (120) Air corrector 180 (165) Emulsion tube F16 (F16) Idle jet 50F9 (45F9) I also found changing to a 50F9 idle jet cured the spitting. Changing the main jet and air corrector made the car more tractable and largely cured popping and banging on the overun. Setting the float levels very carefully reduced the flat spot but has not completely eliminated it. I set the float level (with the carb cover held vertically) to 10mm Min and 15mm max. This gives a fuel level of 32mm from the top of the body to the fuel surface measured on the shallow (engine) side of the float chamber. Boring out the venturies from 32 to 33,34 then 36mm has made very little difference. At 32mm it pulls like a diesel,lots of grunt but no top end, at 36mm slightly less grunt, slightly better top end. I have the old style O-ring seals between the carbs and the manifold, with seperate o-rings each side of an aluminium carrier. I have changed the o-rings to Viton ones. I spent a couple of hours setting the gap between the head and manifold as equal as possible using feeler gauge stack to ensure the o-rings were clamped uniformly. Finally, I was not impressed with the Aldon distributor fitted. When I removed the springs from the counter weights, the movement was very sticky. The pivot holes were not a very good fit and weren't very square to the face either. I drilled them oversize and made some brass bushes which were pressed in place. One weight acts against the other and has a cam profile. The surface of this was very rough, so I have polished this to achieve a smooth action. I like to think it now works properly. The springs weren't right either. They started to advance at about 1800rpm and were still advancing at 4000rpm. My car runs a lot better now than when I first got it. Its always been a bit temperamental when it gets very hot and is prone to stalling at tickover. I hope that this might be of some help to you. Jim