I had one and it was convuluted. One more pickup with a chance to burn out, and I had to modify things when switching to a single pickup. Convulted. Yes.
Switching to single pickup is easy, just unplug the 2 pin connector from the start/run relay then either remove, or move the start pickup out of the way. However, if I were to do it, I'd just remove the relay and splice the run coil to the ECU.
It was emissions related to help passing the tests along with the air pump.
Not true, see the attachment below.
You have it reversed with the distributor function. They had a shorter slot to limit the total advance. This alone stopped total timing at around 36 degrees when setting idle at 10-14 degrees...Which was the same as single distributors.
Actually, there is less total advance with this distributor than a single pick up. Plus with shorter advance slot, the springs didnt bounce as much, to assit with emissions and efficiency. This is like my 440 race car set up. You can run more advance at idle _more efficient for emissions, and then with the shorter slot, this limits total timing for which Mopars do not need. Same with a 440. they like a lot of initial advance, but not so much total advance. The timing gun also showed great smoothness when revving up the motor with the limited slot advance.
No, I don't have it wrong. It's really simple, the two pickups are just mounted apporxiamately 180º apart and the start pickup is mounted to be slightly retarded compared to the run pickup. Again, this allowed more advance in the run position, without causing hard starts. Dual pickups had nothing to do with timing advance, if some of those distributors allowed for different amounts of timing, it wasn't because
of the dual pickups, as their function is ONLY for the purpose I stated as well as the picture from my FSM.