After reading another topic about an air stack on a HP 18-36, I have become interested in finding out more information about the stack, etc.  I have a 1930 18-36 model I, and for as long as I have known the tractor (it has been in the family for years but only recently running again) there has been no air stack at all.  On the carburetor, there is only the round piece that bolts on top of the bowl and sits horizontally (with a circular opening on the left side where air is taken in).  This piece comes an inch or two off to the left side of the carburetor and the hole for the air is about 1.5in. wide or so.  The carburetor has no air stack attachment from the carburetor.  Is the tractor supposed to have some kind of air stack?

Thanks for any help/recommendations.