I knew that blowing into it does nothing and sucking on it (that doesn't sound good
) retards it. I figured that out when I dismantled it to clean and lube it. I was just curious if the only reason is for the vacuum retard was for emission control or if there is a mechanical need for the retardation. My understanding is that while not in boost (vacuum on the canister is overpowering the springs in the dizzy) the timing is held in retard by the canister and when boost develops there is no longer a vacuum to hold the springs so due to their natural tension they return to their normal advanced postion. Is this correct?