Timing was steady at idle, maybe plus or minus 1/2 degree. I had a vacuum gauge hooked up to both manifold pressure and the carb advance port time. Manifold was 9-10 and fluctuating, vacuum port pressure was 0-3 degrees depending how I was playing with idle screw but even at 3 degrees, timing was steady and did not move. Advance started pulling in when I got to about 5 inHG at vacuum port.
Do you mean 3 inches of vacuum at the ported spark fitting? That should be 0 at idle. But steady timing mark is good. Sounds carb related but fluttering intake vacuum signal could be a valve or lash adjustment.
