dist drive question

Took my Dart out sunday with rebuilt motor, decided to time it at the track. Car ran quite a lot slower than expected.
Timing was way off, i suspect the dist drive needs knocking back a tooth.
The car ran ok but ran on a little when switched off, also it was lighting the carb up at times
Could 1 tooth on the gear make that much difference, i'd say it was at least a second off maybe more.
Mike