I guess I can infer you had a light on it. Maybe one of those new adjustable strobes that let you dial in the advance and just look at the zero mark on the timing cover.

Anyhow, I'd be very happy if my old distributors only jumped around a degree. You're right, the B23 has a solid crank pulley, not a vibration damper like the B230. But your valve timing could be off. A foolproof way to check that is by the mark at the top of the cam gear.

If you're not in a real hurry to save the 83, but just want to keep heading in that direction, you might wait for jimo's trial swap to see if he gets results like you do, when he uses one of the plentiful 85-88 distributors in his 83.

I take it you've seen the distributor curves for the 83/84 V/C ignition? That "sudden kick in" you speak of reminds me of them. I was thinking it may be more noticeable if you're starting from a late baseline timing:






--
Art Benstein near Baltimore

Experience is something you don't get until just after you need it.