Engine running away after carb rebuild....

Rebuilt a Holley 1920 to replace a damaged BBS on top of our 170. Had lots of problems with the BBS, likely caused by vac leaks etc. The new carb is much "tighter" and the car starts right up, but then runs like it's wide open throttle (though it's not) until we cut it off. Float adjusted properly (tested the float beforehand) and nothing coming out of the vent tube to feed the engine from the top. Where else would the engine be getting that much fuel from this carb to run out of control?

Even though the BBS gave us problems starting, the engine ran semi smooth and didn't run away like this

Any ideas are appreciated.

-=C