The instructions for my antique, 50s era Loadomatic dual-point conversion kit recommends using a new "long-sweep" rotor. Anybody know when (or if) the rotor contact design was changed, and why?

6 VOLTS/POS. GRD. NW INDIANA

Daniel:

I seem to remember that some rotors had a straight connector from the spring to the tip where the spark jumps, and some had a T shaped connector, which I guess could compensate for an advanced or retarded condition between the distributor cam and the rotor tip.  The cam is machined with the rotor slot in it, so I don't see how it could get off though.

John - "The Hoosier Hurricane"

I think the "T" tip is the thing - Hoosier is right on it - the underside of the 8 cylinder distributor cap has a "pole"(?) every 45°. As the rotor turns inside them, the advance mechanism moves it in an arc relative to the inside terminal as each spark pulse is triggered. I've got mine set at 13° of distributor mechanical advance, so as the engine speed increases the rotor keeps "advancing" - adding 13° of lead to the position where the spark occurs. The width of the "T" nose of the rotor and the width of the pole inside the cap helps decrease the spark gap under the cap. 

 
 Steve Metzger       Tucson, Arizona

So, the old "narrow-tip" rotor would not allow the engine to run at all if timing was too far off? Would make sense if the points opened after one rotor/cap contact and closed before the next.

6 VOLTS/POS. GRD. NW INDIANA