Factory Vacuum Advance Canisters are adjustable. A 3/32 allen key inserted into the hose nipple.
Now the problem is I don't remember counter clockwise or clockwise to increase vacuum or decrease the amount of travel of the diaphragm movement.It can be checked using a dial back timing light.This is if you are experiencing pinging at part throttle.Common when re-curving the distributor using lighter springs.
It is best to use the Vacuum Advance on a street car.