As I have read it, one of the Mercury assembly plants was near the Carter factory and it was the only plant to get the Carter WCFB’s. They were difficult to get to work properly with vacuum secondaries and possibly the Load-matic ignitions and either Ford or Carter requested a stop and they quit manufacturing them for Ford. I’ve enclosed photos of a 56 Merc Carter #2361SA and what I believe is a 57 Lincoln 2404 SA but might be a 56. You can see on the Merc the econo valve on the front and the Lincoln doesn’t have one. Both have the clean air grommet on the left side and the vacuum secondary actuator on the right.
I’ve removed the photos since they cover over the narrative. Many do not know Ford Products used Carter 4 barrels prior to 1957. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

The original post was by John (Old Teacher) who had the ’56 Merc WCFB  carb.  The later post is by Ralph (rponfick) who is simply asking about the choke tube going through the ECZ-B manifold which would be the ’57 and up intake.  Ralph likely has a newer carb and not the Carter WCFB carb.  Ralph can likely clarify that for us.

With all that being said, the choke air transfer tubes going through the exhaust passages of the 1956 & 1957 intake 4V manifolds are designed to move only clean air through them and not exhaust.  If that tube become corroded and/or damaged, then exhaust gases enters that tube and makes its way to the choke assembly.  That's always detrimental to automatic choke performance.  The drivers’ side (left side) of the intake manifolds would be the air inlet and the passenger side (right side) would be the exit for that same air.  That tube going to the air cleaner horn in the picture submitted by John (Old Teacher) would be the inlet for the choke air and it’s there to ensure only filtered air goes to the choke.  You will find a similar inlet air tube on the Holley 4V Teapot carb applications also.  The 1957 ECZ-B intakes simply had a small bonnet or air diffuser for the air inlet for the choke and that was mounted directly at the lower left side of the intake by the heated crossover.  By design, the exhaust heats the air going through that tube as it travels to the automatic choke assembly located on the right side of the carburetor.  Starting in 1958, that tube was eliminated at the intake manifold and the choke air then came directly from the exhaust manifold where the exhaust manifold had a small chamber to heat the air before going to the choke.  Exhaust gasses are still isolated from the choke air.

Lorena, Texas (South of Waco)

I apologize for hijacking this thread, I should not have done that.  I will start a new thread regarding my crossover tube to keep from confusing the discussion.  

Thanks, Ralph