You think that you have your classic after a thorough restoration, service or inspection completely done, you drive it, the thing appears to respond nasty to the accelerator pedal.
Withholds, jerks, knocks and also a high fuel consumption. Then back again, because that must be the ignition. Check everything once more, adjust the dots again and then a test drive again. Nothing has changed. Then it must be in the carburation. Disassemble everything again, completely strip and build up more precisely. Unfortunately, that action also did not help. Well, then why? Look no further, we have the solution (at least if all the previous items are in tip top): the spark plug cables. You have allowed yourself to be lubricated: from those modern, disturbed spark plug cables. They give the spark of your ignition so much resistance, that only a very small spark remains with the spark plug. That is possible for modern cars, but not for a classic car! Go for spark plug cables with copper core and your problem can go into the history books! Adjust the carburetors again more economically ...