One more post for me in this thread, and probably not going to be a popular post, as the information is not what most wish to hear:
These carburetors missing tags CAN be identified! I can identify them (well, I could have, before I got rid of all my B castings), and if I can, I am sure others can as well.
The problem is, if the carburetor cannot be identified by a stamped number in the throttle body, or the casting information I sent to John who has subsequently posted; then the individual must cross a special bridge from the state of rebuilding to the state of restoration.
This bridge has a name; its name is MONEY!
Probably half the cost of restoring a 6 cylinder Chevy carb, or more commonly, a flathead V-8 Ford carb is documention and research.
Why these two? Because carburetors (the Rochester B with the Chevy and the Stromberg "97" and Holley "94" with the Fords) enjoyed LONG production runs with multiple changes in castings, calibrations etc.
After doing a restoration on one Rochester B for a good customer of other carburetors, I quickly decided I could not charge enough to break even, let alone make money; but I have done loads of the Ford carbs.
Enter the commercial "rebuilder" into the picture
So today, the commercial "rebuilder" is going to "rebuild" Chevrolet 6 235 and 261 carburetors (from the "rebuilders" standpoint, these are interchangeable). Whatever the number required of these IN ALL YEARS IN WHICH THE CASTINGS ARE SIMILIAR are disassembled; throttle shafts go in a basket, throttle bodies go in a different basket, bowls in a third basket, and so on. The parts in the baskets are cleaned, bulk parts such as gaskets, pumps, fuel valves, jets, etc., are acquired from the "rebuilders" bins and laid out in an assembly line. The fuel valve will be the largest orifice used in any of these carburetors; the main metering jet will be the largest used in any of these carburetors. The baskets go down the assembly line, a part is removed from each basket, and a carburetor is assembled.
When doing the Ford carbs, we used to figure if we started with 10 "Holley" model 94's, there would probably be enough castings to correctly do 6 carburetors. If the source becomes 20 then maybe we would get 13.
So the above is the definition of the problem, how is it solved:
When restoring the carburetor, the restorer first completely disassembles the carburetor. Now the Rochester factory bill-of-materials for the carburetor in question is located; and body part number are written down, and new old stock bodies are checked from the restorers inventory to see that the casting numbers are correct. This doesn't mean the casting is correct, but it is a start. If not, the proper castings must be found. Now all machined calibrations (idle tubes, idle bleeds, restrictors, etc. are MEASURED, and compared against the bill of material. At this point, castings are cleaner, steel items are cleaned, and factory finishes (the body is zinc chromate, the screws, depending on year will be black oxide or yellow zinc) appliced. Finally, CORRECT main metering jets, fuel valves with the proper orifice, pumps, gaskets, etc. are removed from and the carburetor is reassembled; and a new reproduction tag (stamped out by the restorer) is applied to the carburetor.
I have probably forgot something, but the main points I would like to stress: (1) factory documentation is crucial, and (2) an inventory of new old stock parts for comparison is equally crucial.
And please remember, I no longer perform this work.
From a history standpoint:
In the 1930's, commercial rebuilders (note: no quotes) rebuilt carburetors starting with only the same numbered carburetor. Why did this change? Again, money. As cars began to last longer, the FLAPS had to have increasing larger invertories (read larger buildings and more cost). The FLAPS costs were passed on to their customers who complained about the costs. So enter a couple of "rebuilders" that started "grouping" carburetors; and cut-rate auto parts stores that started selling these cheaper units. And the rest is history.
Jon
