It advances the timing with the application of high vacuum, such as when idling or light accelleration. It should release partially at high rpm operation, the mechanical advance is in operation at that point. Seems to ma that if it's pulling in and holding under vacuum, it's ok. You should try checking it on the engine by having an assistant operate the throttle as you watch the action of the advance. It should pull in imediatly when the engine starts, then release as the throttle opens up.
