Spent most of the winter replacing brake lines etc. on my old VW. (Didn't I just do that 20 years ago?) Finally got the Buick into a garage with some heat. Went through the brake system cleaning & lubing all the clevis joints and setting up the linkages “by the book”. Looks much better & pulling each wheel with a fish scale shows pretty equal loads. Overhauled carburetor. Thanks Hugh for the rebuild procedure. Thoroughly cleaned everything and did some rework on the venturi. Float worked so was resealed with POR-15 All was going fine until I tried to do the shop set up on the air valve. With air valve screw flush with the end of the ratchet spring, there was a load holding the valve shut. Discovered that the spring looks the same as the one in your procedure except it is 2 inches long not 1-1/2. It has been stretched. I set it up to the no load gap shop procedure. When I took it apart the air valve screw was halfway in from the end of the ratchet spring, so the air valve was probably inoperable. In the meantime I need to identify the carburetor.The body is pot metal and has three jets instead of the 2 that you show, see photo. I can’t order any parts until I know what I’ve got. Any help would be appreciated. Went through the fuel system and replaced all the gummy pre-ethanol rubber hoses. Replaced pressure regulator and filter. Adjusted carburetor fuel valve per spec. On startup, had to readjust air valve to normal flush position and it worked fine. Idle is ok but doesn't sound good in exhaust. Suspect exhaust preheat leaking and needs to be blanked. Runs good yard, see what happens on road.
Lastly Bill to answer your question, I learned some history. This car was “HOME BUILT” by the original owner as a hobby over the course of many years and was first registered in 1980. To summarize the description given to the present owner:the front clip is from a coupe, center section is from a 2 door sedan which provides wider doors and the back clip with rumble seat is from a special coupe. Other parts came from junkyards and swap meets and it is all 1929. The guy did a commendable job. I’ve recently spent a lot of hours under this thing and it is cleaner than my own 3 year old car. Not a pedigree but a real fun driver. Just want to get it mechanically fit. Wheelbase is 116 and engine VIN number and location indicates a 310 engine.