Replacement vacuum advance can for 318 distributor

It dawned on me tonight, I can swap the Pertronix onto the electronic distributor Ray (halifaxhops) curved for me. Just had to swap the top plates, because Pertronix only mounts to the points-style plate. Also had to drill the inner hole for the curved-arm style vacuum can that was on the distributor.

Hooked everything up, fired up fine but I have a really erratic timing mark at idle. Appears to jump all over the place by a couple degrees at 650rpm. My idle is somewhat erratic, seems to have a miss or something. Possibly ignition related, not sure. My idle quality had deteriorated somewhat before getting into the distributor, so it may be unrelated.

Set initial to 17 (mech 20) and did a brief run, car felt strong good response. Good enough for tonight.

I will work on diagnosing the erratic idle tomorrow. Not sure why my timing mark would be jumping all over the place. I am using a digital dial back timing light, but the sound and feel of the idle seems to agree with what the light is doing.