Whatever timing it can hold and still run cool enough not to seize.
Points and static timing start at 15.5 degrees btdc and add or subtract timing until you stabilize at around 380-390f head temps @WOT.
Hpi/curve ignition around 2.2 mm btdc in the plug hole to start and add if you run cool less then 400 degrees bla bla.
With points or static no curve cdi you may not be able to stabilize temps 400f degrees at head if your running big and or high rpm pipes .
Cdi with retard curve may be needed.