rebuilt 301 vibrates at around 3k RPM or 40 mph

[Rusty Muffler]

Presuming you have the point dwell set at the correct value and point gap in similar, what does the dwell look like the rpm the roughness starts? If you unplug (capping the vac line unplugged) the vac advance, how might that affect it?

Might need to seek out an older repair shop which might have one of the ignition oscilloscope items to watch what the spark plug firing/ignition system is doing. That would quickly identify which cylinders are having issues or if all of them are contributing. As to what the ignition system is doing.

Just some thoughts,
CBODY67

Thanks CBODY. The problem is more in the 2k rpm and above and the dwell was off about 2 degrees at about 33 degrees. I adjusted it to 30 degrees at idle and it moved to 23 degrees at 2k rpm or above. The advance seems to be working as it drops about half of the advance timing off when disconnected. The timing light strobe light is steady on #1 at any rpm. Also the vacuum is in the green but has a high speed jidder. So compression is all even at 100, choking the carb did not help, the plugs look grey (maybe too lean?), none close to black. I have one of those gismos you hook at the spark plug that flashes and it shows the wires are good at any rpm.
Fuel?

 

[CBODY67]

Lean is chalky white. Good is white to beige. Never have seen gray. But he carb is for the engine, it's probably ok.

 

[furious70]

Sounds like you have vacuum advance hooked to manifold vacuum and not ported? Is that on purpose? Or were you not talking at idle?
Too much timing even at light throttle can cause lean surge/miss

 

[Rusty Muffler]

Sounds like you have vacuum advance hooked to manifold vacuum and not ported? Is that on purpose? Or were you not talking at idle?
Too much timing even at light throttle can cause lean surge/miss

It's ported at the base of the carb. I know this because I hooked the vacuum gauge to it and only shows vacuum at higher rpm's.

 

[furious70]

It's ported at the base of the carb. I know this because I hooked the vacuum gauge to it and only shows vacuum at higher rpm's.

What were you describing when you said the advance drops when you unplug it? Not idle?

 

[Rusty Muffler]

What were you describing when you said the advance drops when you unplug it? Not idle?

No, nothing happens at idle when I remove it. Only above idle does the timing advance more when I reconnect it.