Searching out a weird running issue, part 3

Here’s where I’m at. Still no joy.

Hooked up a Mityvac at various places (not much to check since most of the vacuum lines are capped off now). Brake booster holds vacuum nice for at least 10 minutes, figured that was long enough for a test. When I connected the Mityvac to the main manifold port, the gauge bounced all over, which according to what I could find indicates a weak or broken valve spring. Very possible, but I don’t think that’s the cause of my issue.

Used a can of spray carb cleaner to try to search out vacuum leaks around the carbs. None that I could find.

Double checked the oil in the Strombergs. Definitely full, and the plungers seem to move very slowly like they should. I still wonder if heavier weight oil might make a difference (I just used the same 20w50 that goes in Ms. Jenavieve’s crankcase) but I have a hard time believing that this is the issue since this is the same oil I’ve always used.

I also, when I had her out this weekend, experimented with different choke settings while driving (when I came to a stop, I would pull the choke a little bit before taking off).   Other than raising the idle, it didn’t seem to make any difference, I still had the hesitation and backfire.  So I really don’t think it’s an issue of being too lean under those circumstances.  If anything, I think it’s too rich which takes me back to ignition…

I still haven’t done a compression test, but I don’t think that is going to solve anything (other than to point out other unrelated issues). I guess I’m at the point where I call Delta and order the Pertronix distributor and coil.