Mike - I am the current caretaker for existing records of both Carter and Stromberg carburetor companies; so I do have access to data not readily available elsewhere.
As far as the base stamped numbers are concerned, yes the 321 is found on about 25 percent or so, and the exception (there are others) to the leading number being omitted.
The reason so many W-1's (and other Carter carburetors) do NOT have the bottom stamp, is quite simple......the commercial rebuilders. When many of the less-than-top-quality commercial rebuilders would rebuild a carburetor, they would machine the bottom casting (whether it needed machining or not) to remove any possible warpage (cast iron is so prone to warp
). It was a time-saving move. Less time was involved to simply hold the casting up to a grinding device rather than hiring someone to check for truth using a feeler gauge.
As different carburetors proliferated, common also for these rebuilders to "group" a number of different carburetors together in one "replacement" number, throwing away the tag, and also grinding off the stamped number so an intelligent customer would not know they were NOT getting what they thought they purchased.
Jon.
