Think of it like this. Take a dist and have someone hold the dist shaft so it wont move. Then grab the rotor and turn the mech advance all the way and line up the rotor where the cap terminal would be with the advance fully advanced. Then have the guy holding the dist shaft let it go while holding the rotor lined up to the caps terminal spot. The advance will move the dist shaft backwards when its let go but the rotor wont move. Then have the person move the advance forward through the advance while still holding the rotor , reluctor and cap terminal lined up and you will see the rotor stays lined up with the cap terminal all through the mechanical advance travel. Its the same thing when the mechanical advance goes through its travel as like I said before the rotor , reluctor and cap terminal will still line up only it lines up sooner since the mechanical advance has come into play. Ron