318 Engine stumble

Reversed polarity does 2 things:

• Puts the pulse edge out of sync with the rotor because the physical relationship is now wrong for the assembly
• The correct polarity pulse edge is quick and sharp and produces a very stable pulse off which to trigger. The wrong polarity pulse edge is generally slow and that creates some ambiguity on the trigger point; the timing gets a bit unstable.

Just trying to figure out your post #94 causes.

Again if you could post your distributor info, that would help.

And if you are suing a dial-back timing light, I would borrow another one and see if that changed the rotor timing situation. Dial-back's are know to show errors with certain ignition types.