The stock vacuum advance distributor is connected to the carb/manifold by a small rubber joint that in turn is mated to metal line that fits the distributor! If the little rubber connector is deteriorated it could allow a vaccum leak at the carb and stop the advance from working properly! the rubber connector is straight. When in doubt- replace it!
See 12B2062 for the angled connector, 37H4229M for pipe and VAC001 for a kit of all three. Also fits Sprite , MG Midget , and Morris Minor .