bouncing timing mark

OK. You guys got me running REALLY good. Timing fine, re curved distrib. All seems to be well, except..... My TDC mark on my damper bounces around when timing the thing. It's a 509 really only bounces about 6 degrees back and forth. Can't figure it out. Can't tell EXACTLY what my initial is.
I've had some pretty radical cams in GM products and when setting timing at around 1000 RPM, that mark was steady as a rock. What gives?
Author: admin