Vacuum reading help.

BillGrissom said

I agree with Redfish that most likely the vacuum pulsation is due to mis-fire. My 69 Slant was like that for years, and mechanics said "bad valves", "vaccum leak" and such. Turned out it was the carb and a ~4th one made it run perfect. That was a Holley 1920. Your Carter BBS looks easier to diagnose (have one on my 64 Valiant).

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Were you ever able to figure out exactly what was the carb issue?
I read some other threads regarding what you are describing so I had initially tore apart the carb, cleaned, and rebuilt.

I've heard the BBD's were prone to worn throttle shaft bushings which caused vacuum leaks, but haven't heard this about about the BBS.

I'm leaning toward some form of valve-related issue but curious to know what exactly was the carb issues you had were.