Rebuilt 318 install problem

I had very similar symptoms to this on my 318. I found that I had neglected to fit the spacer plate between the carb and manifold and I was getting a vacuum leak between the two. Looking at your video it is hard to see if you have the plate installed and I think if you are running an edelbrock carb you have to have the plate fitted as well. This is assuming that your manifold has both square bore and spreadbore bolt holes.

Cheers
Anthony