Rochester used at least 2 different threads depending on the year.
If the carburetor still has a tag, one could look up the original part number, go to the bin, pick up a screw, and measure the thread.
OR
One could take one's micrometer and pitch gauge, and measure the screw one has.
A micrometer and a thread pitch gauge are two tools no enthusiast of older vehicles should be without.
As far as what to do; my first reaction was: its a Rochester B, why bother?????
But to promote information, in the past we have on various carburetors worth saving:
(1) Used a heli-coil where there is sufficient "meat" in the area to rethread (MSC has the 10x32 Heli-coil kit for $72., how many threads are you going to repair). I can happily report I no longer have a single Rochester B to examine to determine if sufficient material to hold the Heli-coil
They have ALL left the building!
(2) Rethreaded the hole to the next larger diameter with the same thread pitch, and made a new screw on the lathe, if we didn't have one. This I would consider ONLY if no Heli-coil were available. And the customer would be notified before hand, and given the opportunity to say no.
(3) A home enthusiast MIGHT get by temporarily with a longer screw of the same thread/pitch, but not a repair we could, or would, use in the shop.
And while it is certainly possible for an original screw to gall, and strip out the zinc alloy; there are number of vendors selling "dress-up screw kits" which use stainless screws. Stainless screws should NEVER be used on zinc alloy, unless one enjoys repairing stripped holes the next time the unit comes apart. Not throwing this at the OP, simply imparting information.
And just for the record, we have tested every epoxy sold by all local FLAPS, as well as tested the miraculous pot metal welding rods (I knew better than to try this myself, as I know, and respect, my welding limitations; we had a professional do the testing). We were not satisfied with any of the above for a professional repair, although an enthusiast MIGHT use one of the epoxies as a temporary repair. I don't consider the pot metal rods even suitable for temporary (at least on carburetors).
In this case, if the OP is really in love with the B, I would suggest just finding another exact replacement body. The B's simply are not that expensive. It took me 25 years to get rid of all of ours.
Jon.
