Could a wrong advance setting...?

[panic]

...create over-fueling and an engine rough running?

Also, once setted the advance and screwed well the dizzy, can the setting change unexpectly by itself?

[steve-V8s]

Can’t think how the timing can have an effect on the mixture. However if the timing is so far off as to cause a misfire un burnt fuel will be in the exhaust gas so it could smell as if it is over fuelling.