As best I can tell, that Model B is 1-9/16" throttle disc, 1-11/32" venturi flowing about 200 CFM @ 3.0 Hg".
The Ford 32/36 is about 270 at the same vacuum.
Something is wrong, but it's not too small.
I see you checked the linkage position; are you sure the secondary throttle is actually WOT?
Are you sure the power valve is open?
