I would want as much vacuum in the can as you can find. It has zero effect on how much initial you run. The vacuum can falls completely out on acceleration. It's only purpose is to clean up unburned gasses on part throttle or no throttle conditions and give "a little" advance at cruise. The amount of vacuum in the can should be completely ignored when timing an engine.
Yes, I'm not sure what I was thinking. Anyway, I have moved on from that, have my Halifax hops distributor with good vac can on it converted to a Pertronix and now I am trying to diagnose a misfire or related issue at idle.
Swapped to an old coil, had the same issue. Took the car out for a run, runs beautifully but didn't want to idle. 0-60 was the same as before, on wet pavement with a lot of wheelspin which I take as an indication the new distributor was an improvement. Oddly, after a full throttle pull the car returned to idle and idled very smoothly, the issue was gone. Then as I pulled back into the garage it got rough again and even backfired.
I think I can safely say at this point this is related to the ignition system. I soldered connectors onto the Pertronix, but there is no way to test the connections. I double checked the gap on the reluctor, its 0.030" as recommended. Something is making my ignition very weak at idle.
The coil I swapped in might be marginal as well, measured 1.5 primary and 8.5k secondary but who knows with bench tests. An ignition coil is an expensive item to buy just to rule out an idle issue.
