Not sure what carb that is, other than not an Edelbrock one.

In this article https://www.hotrodhotline.com/conte...barrel-jim-clark-hot-rod-md#.X68zjhZ7mM8

It states "Vacuum from beneath the venturi in the carburetor has drawn the piston down in the choke housing keeping the choke butterfly open once the engine has reached operating temperature."

Doesn't sound like it should be a vacuum leak. If I remember I;ll look at my carb tomorrow and see if it's open or sealed.