Sounds like a stuck float/needle/seat. I had an old Holley that used to do that from time to time. I used to carry a screwdriver with me so when it would I'd just get out and give it a few "taps" on the front fuel bowl and it'd be ok til next time... One of the few reasons I quit using Holley carbs.
I still have an old 600cfm Vacuum secondary sq. bore in the garage.. for old times sake.
