If the adv is connected to the intake it will be at full adv at idle and slight throttle if the adv is connected to the carb ported vacum supply then it will adv as engine speed is increased so you will have to see what sys you have..most GM,s back in the late 50,s and 60,s used the full vac,,,FOMOCO used the ported as did 216,s and 235,s...later flatheads had no mecanical just vacum...doc
