Classic/Antique Car Repair: tining, chevy 327, vacuum advance

Question
Brad,
 I have a 66 chevy, 327, 350 hp engine, I believe I have a timing or electrical issue. I installed new plugs,points,condenser,coil. I have set the dwell at 30 degrees, set the timing at 6 degrees at idle and it seems to run smooth. However when I accelerate slowly at about 1300 rpm I get a slight miss to about 1700 rpm. The timing light indicates the advance at 1500 rpm to be about 44 degrees. Any suggestions on what the problem is? I am using the original distributor that has about 70,000+ miles on it.

Answer
This is right about the change over in the carburetor from the idle circuit to the high speed circuit and is noticable under a no load condition. I think that if it were me I would start by looking at the float level in the carburetor. It could also be weak springs on the centrifugal advance on the distributor allowing the timing to advance too quickly or a weak spring in the vacuum advance.
Brad