I think it's an exhaust -- for the kitchen sink.
It looks like something to convert the updraft to downdraft.
I think it converts side draft to down draft or vice versa.
The lower flange does fit a Fronty single port head and in this position the carb. would be way above the hood. If flipped it would be low to possibly clear the stock steering? I don't think either application would work well with that long run and 2 bends. It might run OK but I think it would be a problem to start.
I really hoped someone would ID it as something else and it could be reunited to the proper car (like a Auburn or Cord!). I tried the kitchen sink but PVC works better.
Tim if the 180 degree sweep was hooked on to a 90 that was coming off the head facing up, with a side draft carb on the bottom I think it would fit nicely. That also would make it very close in length to the 17 inches Ed Winfield, Jim Cullinane and Humble Howard talked about. I believe it referred to the Himholtz (?) effect. I would not want to be hand cranking it to get it started.
Are you cleaning your shop today?
Are you sure that it's an intake manifold?
Could be a water inlet/outlet pipe for another make early car?
In the photo, at the top right just above the flange if it was turned to look sideways there is a drilled and threaded hole that I assume would be to prime (or a vacuum line).
John has an interesting thought as the bottom flange is ground out like a funnel but the top flange is flush. I don't know if this indicates that a carb. would go on the lower flange and I am not familiar with the "Himholtz effect" but that would make the assembly look sort of like the intake on the 2 up 2 down or the intakes that Mark makes for the new Rajo heads but only half of one.
Really I have no idea what it was made for, yes John I was sorting around in parts this weekend trying to clean up a little.
Any ideas on the valve cover photo I posted? I thought Aaron might recognize that. Another mystery part I can't throw in the scrap bin but have had it for years and don't know what it fits.
I think the AACA forum still has a "What-is-it" sub-forum. Might be a good place to post the photos?