base timing keeps advancing by itself...

cudamark said

Yup, a slipped balancer wouldn't effect the idle speed. Sounds to me like the point plate may be moving around. Any play in it or the Pertronix pieces? The only other thing I can think of would be the end play on the camshaft is way off, or, it's thrust surface and/or plate is badly worn or missing. What does the timing look like with the light? Is it steady and smooth when it's advancing, and returns the same way?

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Just tore into the distributor, point plate seems securely fixed by vac-can. When vac is applied, it moves smoothly, snaps back when released. There is some minor corrosion on the weights, but everything seems to be good.. roll pin is intact and not sheared, I just don't understand what is going on here. Im going to put a little grease in the advance slots.. but there is not anything that looks out of order in the distributor.

Timing with the light is a little erratic.. bounces back and forth maybe 2degrees at idle, mark seems to steady at higher speeds. Bounced way more (like 5 degrees) before I installed the shaft collar on the distributor. Still, very minor movement of a few degrees.

The camshaft was installed (and whole engine built) by 3rd party supposedly reputable machine shop. I guess cracking into the motor to check end play, camshaft, timing chain etc will be the absolute last thing to check.

This is a real pain in the ***. The car runs so well when the timing cooperates.