set your base timing by posotion of the distributor
use vacuum advance if you need more advance at higher rpm
it uses a ported vacuum source on the carb
mechanical advance also works at higher rpm
alot of times i dont use vac advance, i dont even connect it, especially on stock cam engines,
as they run perfectly fine without it and get plenty enough advance from the mech weights already
to run fine.
overkilling ignition advance will cause problems quicker and worse than not having enough .
due to detonation/pinging from over advanced timing
use a timing gun to figure out your base timing and to see how much your advancing at what rpm levels
too much of it is the worst thing to have.,,