Old hat...

mbaird said

your wandering vacuum at idle may be due to the light springs in the mechanical advance.
I just recurved my dizzy to a slower advance curve that applies the last 5-6 degree over 3k slowly. After a short drive my car seems to like it. A longer test mey prove me wrong....?

Click to expand...

I wasn't clear. The 'dither' part is when I've used manifold vacuum. I edited the post to reflect that.

I have had idle settling (with an 'l'..NOT 'setting') problems in the past, but that was resolved with a drop to an 800rpm idle (Hughes' advice, I had been set to 1000) and, back-when a bit, stronger springs just as you said. Having any active advance, mechanical or vacuum, in play at idle speeds doesn't work.

I'd have to check my notes to be sure but mechanical doesn't start until around 1500rpm. Another tip from Hughes: Mechanical advance should start no less than 400rpm above idle. Sounds reasonable.

I don't pretend to be a tuner with mad 'skilz'. Not at all. I understand what I read or what I'm told but, when it comes to, 'This is the problem: Fix it!', I'll be doing a good bit of dithering myself.

Thanks for all the input!