On carburetors, if they have ever been through a commercial rebuilder for any reason between simple freshen up to show preparation almost anything is possible.
One friend paid an insane amount of money for a very low volume high performance Ford 4100 model from a world famous shop.
1) His car's engine would not idle at low rpm with it installed.
2) Idle mixture tuning could never be done well even though the transition slots were not exposed.
3) Multiple mechanics in multiple shops tried to tune it without success.
4) For some reason somebody had been welding up something on the mounting face and crudely tried to true the surface.
I rarely work on anybody else’s carburetors anymore but he begged. What I found:
4) Both threaded ports for idle mixture screws had been welded up, redrilled, and rethreaded. The threaded holes were so large the needles could be wiggled. The threaded joints leaked, no surprise. Might have been where the extra air at idle was coming from.
5) One idle mixture screw didn’t seem to align with the passage the needle tip belonged in deeper in the body.
6) The flange area where the original assembly identification was stamped had been welded over.
7) The freshly welded flange was machined with a end mill and left lower flatter than the original casting shape.
8 ) The number of the model my friend wanted was stamped there and then lightly media blasted to age it a little.
9) The primary and secondary venturi clusters were from standard (not enriched performance air fuel mixture) model.
10) The main jets were for the same standard model.
11) Neither dry float setting was anywhere close to what they would have been for the performance model.
12) Every screw and or washer in the assembly was something brand new that only resembled anything original at a distance.
13) The choke settings were no where close for the model my friend was hunting.
What my friend had purchased was very expensive assembly of scrap metal with a rare assembly number added for his benefit. Yep, world famous shop can be worse than nothing.