Yea, it should close but not completely.....very close though.
I had a problem with my BBK TB. The bar that runs up the butterfly valve and down to the linkage below busted. It broke where the two screws hold it onto the valve itself. My throttle was sticking bad afterwards. It may be your problem too. Just peak inside the TB and see if that bar is still in one piece. BTW, I never could get a hold of Edelbrock (the manufacturer of BBK TB's) to see if I could just order that piece to replace it. Guess I will have to buy a new one
