Quickfuel problem

[DanEC]

It would be good to have a little more information about your motor. A lean continuous miss at highway cruise is sometimes brought on by too much total advance with a motor with vacuum advance. Some motor, because of their aggressive initial and mechanical advance curves and high compression, can only tolerate a minor amount of additional vacuum advance at cruise speed. The continuous miss is because the engine is firing far enough ahead of TDC that the flame front is spreading sufficiently to cause a slight kick-back which feels like a light miss.

If you have vacuum advance then it's simple to plug it temporarily and run the car. If the miss is gone then that's the issue and you need a vacuum can with less vacuum advance.

An engine idles on the idle circuit but runs at light load on the transition circuit. As load increases the primary jets start coming into play. Most carbs are considered to be too rich in the transition circuit - thus the common need to install transition circuit bleed restrictors. Usually a carb that is a bit large for an engine (like most enthusiasts will install on their hot rod engines) will run rich. If that carb is put on an engine at the upper end of the scale that the manufacture recommends it for - it may run a little lean. Most carbs don't have provision for easy adjustment of the transition system - possibly some of the upper scale units like Quick Fuel do - I don't know.

But, it would have to be pretty lean to actually be stumbling and missing at light cruise throttle. That's what makes me wonder if you have vacuum advance and have an over-advanced timing situation.