When measuring the carburetor float height as specified (Float Level - 3/4" measured from machined surface to top of float--while held upside-down)", is the top of the float, "while held upside down", the surface I'm looking at standing over and looking down on the float, or is it the distance between the machined surface and the first plane of the float (when in the upright position, I would call this surface the top).
I realize this sounds like the 3 stooges, "who's on first skit". LOL.
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I agree with your interpretation. I don't have access to a 1931 shop manual. I know that in the 1934 shop manual there is a picture of checking the float setting. On that carburetor they use a 3/8' rod between the machined surface and the "top" of the float.
That is the way I check them if there is access to insert a round object like a drill bit or rod of the correct diameter.
By the way, "Who's on first" was an Abbott and Costello skit. I don't think the 3 Stooges ever got that sophisticated!