Holley issue

This is fairly common to see on Vac Sec carbs. In my experience anyway....
On a vacsec carb, the secondary's slap closed by the diaphragm spring when you close the throttle, and the fuel flow doesn't stop right away and floods the tops of the throttle blades.
However, if you didn't get all of the way into the secondary's, you could have another problem.
To check this:
With the engine off, open the throttle 1/4 to 1/2 and hold it there. Now check to see if the secondary's stay closed on their own, or pull open a bit. (there's a link that forces the secondary's close at an idle)
If not, there's a couple of things that could be the cause. 1. wrong length Sec diaphragm rod. (too short)
2. Sec Dia spring is not returning the diaphragm to 'closed' (could also be stiff/old rubber dia)
3. and of coarse a binding shaft. In this case, the secondary's won't open correctly either.

My 2¢