Carburetor Bronze Casting Warp Question

[Guest oldodgeboys]

I picked-up two carburetors made for a Dodge Brothers 4 cylinder, a Stomberg OD-1 and a Stromberg MD (c. 1923).

Both carbs have the same condition: the bronze mounting flange ears bow outward from the engine block slightly...about 1/8 inch give or take. Its so consistent between the two carbs that I wonder if the bronze casting was made deliberately this way; after all, the warp would help keep pressure on the mounting gasket and seal the carb against the block (or is that just wishful thinking?).

Has someone seen similar bronze carbs with this type of flange bow?

Should I leave it alone and mount the carb as-is, or try to bend the bronze ears, or make a spacer to make up the gap created by the bow?

The last thing I want to do is break the casting!

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:confused:

[Bhigdog]

I don't have the answer as to why they are bowed but consider: You can do no harm by fabricating a tapered spacer as opposed to breaking an ear by tightening or attempting to straighten. Depending on the age, alloy, or work hardening bronze can be brittle........Bob

[Mark Shaw]

I doubt that they were deliberately made this way. In fact both castings may have been made from the same original pattern. Evidently the mounting flange need not be parallel with the mating intake flange to form an adequate seal. Otherwise, the original pattern probably would have been modified to correct the later casting. These were and made automobiles and not all parts fit together like modern interchangeable parts do.

My 2 cents...

[Guest oldodgeboys]

Thanks for the input Mark, makes 'cents'

I'm rebuilding the OD-1 now since it's slightly more advanced and in better condition. I took the MD (which had just a little more warp than the OD-1) and bolted it to the engine block without a gasket.

Well...the flange just deflected and matched up with the block. No fireworks or regrets, so I think I'm safe with the OD-1.

Thanks again.

[Guest Ken G]

Just to say that I have a very similar carb on my 1925 Rover 16/50 (Stromberg OS-2); it looks very similar to your picture and it too has a bronze body. I haven't noticed any "warp" on the mounting flange, but I wouldn't expect the bronze to have deteriorated or warped in any way, so if there is curvature I think it is deliberate. However, be warned that the venturis inside are probably pot metal (at least, mine are), which will almost certainly have crystallized and swollen, with the result that it is impossible to remove them without breaking them (and they are very brittle). So if they are intact, leave well alone! If anyone happens to have had spares turned on a lathe, probably of aluminum or brass, I am interested!

Ken G, 1925 Rover 16/50 (San Francisco)

[Guest DeSoto Frank]

Ken offers a very important warning about any die-cast zinc ( pot-metal ) bits in pre-Depression machinery.

Early pot-metal had a high lead content, and is prone to "inter-granular corrosion" - the metal "swells" / "grows" , cracks , and crumbles.

As for the bronze bits, I would not try to straighten that mounting flange... get some thick, soft paper gasket material and make some gaskets, sanding them a bit thinner where needed.

While bronze is malleable, castings usually aren't so, and tend to break when you attempt to straighten-out a warp or bend.

I've broken a few bronze castings, even after heating and trying to "be careful".

Good luck !