[Macbuick]

Hi,
On my 350ci is a stock Rochester 4BBL. (El Camino 1971)
How can i be sure that the 2 big barrels chokes (at the rear of the carb) really get open when i drive it ?
Must they be always open as the engine get warm ? Or ...?
The front ones works well but i can't figure how to check the big ones...
Thanks
David