Engine stumbles

I have a fresh 460 installed in a 68 continental. After going trough the initial run in and a couple of small setbacks along the way. (Thanks to some of you) I am having another problem. The engine idles fine and sounds good, Timing and idle are set to specs. When I rev the engine or depress the pedal and hold it steady it begins to stumble really bad, and when I release the throttle it will keep stumbling and barely run and not want to idle. If I shut it down and restart it will idle fine untill I rev it high again. I still haven't driven the car as I am still doing other things to it but I am hesitant to try unless I can figure out what is amiss here. ....................Richard

Could be carb or ignition related....How about a bit more information on what systems you are running and what has been done to them?????

Edelbrock performer intake with holley carb. Ignition is a breakerless from crane cams with a matching coil. It is about ten years old but I haven't driven this car more than a few hundred miles since then and none since the new engine. Maybe time to replace it for a more modern setup?

Could be a sticking mechanical advance.

I will check that Thanks!

R Pope you were right. I checked the vacuum advance and found it was stuck. Replaced with new now the engine revs with no problems. I feel like a total A$$ for missing that. Next weekend I will take it on it's maiden voyage. I can't wait.Thanks again................Rich