1st loosen the dist. hold down just enough so you can turn it,
but not too loose
(disconnect the vacuum advance hose plug the spot off the carb/hose)
start it then set the idle screw up to like 1500-1800rpm
an rpm before the centrifugal advance kicks in
use a vacuum gauge if you have one too, on manifold vacuum to read correctly
turn the distributor until it gets to the highest 'vacuum &/or RPM'
back it off just a tad, check with a timing light, see where it's at
you should be relatively close, for initial timing, your specific engines' needs,
for what your engine actually needs or likes
(every engine, no matter if 'stock' or not, will like a specific timing, distr. phasing,
camshaft grinds even stock + or - 2*- 4* easily & chains or timing gearsets differences
head gaskets thickness/final compression, valve preload, combustion camber changes
altitude, relative air density, carburation tuning etc.
all can & will contribute to 'what it actually needs', not just by the book.)
then set the throttle at like 2,800-3,000rpm, look & see what the total timing is
with the vacuum advance disconnected, it should be like about 34*- 36*, total
maybe 38*- 40* (without vacuum adv.) if it needs that much, especially if at altitudes
*** see below... then return the idle screw to like 750-850rpm,
after the VA is reconnected
drive it & check it out, you may have to bump it back a degree or 2
if you hear pinging especially on a partial throttle load,
bad or old gas can cause that too
*** put the vacuum hose back into the Vacuum advance
with vacuum adv. is fully activated 'at rpm' like 3,000-ish rpm,
it will be like maybe 45*-50* atdc probably,
unless it's limited in some way, but that's not stock if it is
that's how I've done it for decades, never fails
anyway good luck
good luck