Why is one 340 connecting rod bronze color?

70aarcuda said

These are the comments I found on google...

dipped in copper at the factory to bring it into weight specs.
the copper flash plating was to fix rods that got a few tenths too big when they were honing the big end

GM, and Chrysler do it quite a bit, though I cant say I have ever seen a copper coated Ford rod. It was done at the factory to save rods that were finished just a hair too big. Dip them in the copper and you can get them back to the correct size. I do not beleive any rebuilders do it, it would not be cost effective. I bet I see at least 5 or 6 rods each year that way. Does not seem to hurt anything at all.

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ding,ding,ding. winner here. (but not on the weight thing, just the resizing and all big 3 automakers did it, I knew one of the shops owners that replated em and it was a mainly a ford vendor but they did GM and Chrysler too.)
Got laid off at my McGraw glass plant and was shipped to Trenton engine, Detroit Axle and Dodge main for a few years before I could go back to the glass plant so I learned a few gimmicks they did to save money.
I worked at Trenton Engine plant (worked on the rod line for the V8's) running the natco's that did the piston small end right before that went into the broach machine for the big end. If either end didn't make final inspection and was under the .02 oversize limit they went into a bin and when the bin was full it was shipped to the platers to get resized, returned and re-ran through the 2nd and final honing to correct size. Guess what color they were? yup copper. over the .02 limit they went to scrap. some big ends were done due to operator error or just plain dull tooling (broaching them usually either works or tears the crap out of the big end and ruins the rod), but mostly for the small end since the pin is a press fit and needs to be tight.