Dan, the casting number is 6R 2795-B. Looks like they were progressively strengthening the areas prone to warping. This iteration seems to be short lived. You would think the casting number would have changed.
Thanks. It is great to learn a new detail. I have been working on the various 3259 family carburetors since the late 1970s and never seen a main body like yours. (That is why I call all my studies works in progress.)
I would not have expected a number change unless an engineering "C Change" was made in the design. (Here C Change means a major design change creating a new engineering part. Small miscellaneous changes would be just revision levels of relatively minor changes.)
I don't know about metal injection all that much but in the industry I spent 37 years and 1 month in we had dozens of plastic injection molding machines and I cannot guess how many molds. It was very common to have a mold for a new version of a part and then spend the next weeks fixing the product design. Even when finite element analysis was done on the part design, the mold, and the molding process issues at the manufacturing level would often turn up. A very common one was breakage of parts as they were ejected from molds. The tool and die shop we had in house would make radii bigger and very often add stiffening ribs and or gussets not for product service life but to get freshly molded parts out of the molds without stress whitening, deformation, or fractures. Every damaged part was a productivity loss cost in time and money. Adding a tiny amount of material as bigger radii, new ribs, or gussets was cheap compared to lost productivity. Very rarely was it a finished part field failure but they did happen and molds got tweaked some more. The result was a mold with a number and a part with a number molded into it and several drawing revisions. No matter what happened to the mold and part design the numbers stayed the same while drawings for parts and tools changed revision level.
One Cobra part example I illustrate often is the drive end alternator cases for Cobra assembly line alternators. The alternators a 1963 engineering file designation, were introduced in 1963 Galaxie 427 powered cars with transistor ignition, and used again in CSX2201 onward Cobras. The original drive end case design suffered field failures in the form of cracking at screw bosses in 1963. For 1964 model year cases the mold was modified to make the offending areas thicker metal and add two long gussets to each screw boss, the breakage apparently ended. The 1964 version of drive end case has the exact same engineering, sales, and quick reference numbers as the 1963 model year version. "Same" part, two revision levels.
Another Cobra related part was the fuel bowls for E. Weber 48 IDA 2C family carburetors. The original drawings done in 1963 and the early carburetors made in 1964 (and maybe 1965) did not include a stiffening rib in the fuel bowl wall under the inlet. One day new bowls showed up with stiffening ribs and current models made today still have the rib. After studying bowls with and without ribs and marks left on bodies during manufacturing I believe Weber was probably losing some number of just cast bowls just getting the parts out of the die cast mold. I believe, I have no factory documentation, the rib was added to deal with such a manufacturing problem. The Weber part number did not change when the rib as added to the design.
