This is sort of a revisit to an issue I had earlier.
69 Z, everything stock with 140 cam. Before, I had an issue with erradic timing/idle that was chalked up to a tweaked advance spring. Fixing that got it consistent.
Now is another issue that I think is similar in the cause, but not the same symptoms.
When cold, its fine. Once it warms up, if you bring the RPMs up, it slowly
comes back down to idle. Really slowly.
Ive ruled out carb/linkage. No binding, and when you put some load onto the clutch, it brings the idle down and stays there once the clutch is released.
Next thought was that the vac advance was sticking. Disconnected/plugged the vac advance at the carb, no difference.
I pulled the distributor the other day. Everything is moving freely without any dragging or binding. The end play is not too tight nor too excessive, and I dont think
that would cause this problem. The first time I went through the distributor, I set the endplay to Jerry M's specs. After some running time, the endplay had zero slack, so I used a thinner shim.
I'm kind of thinking advance springs again, because it seems like the advance is "hanging". But the springs in it now are out of my 70Z, and it never had this issue.
Anyway, just thought I would throw this out to see if anyone had any thoughts/suggestions, because Ive never run into this issue before.