Why is one 340 connecting rod bronze color?

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dibbons

dibbons

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The hodgepodge 340 I am working on has one 340 connecting rod casting #2899496 which I guess was used on 68-73 340 which is the normal gray steel colro. The other seven connecting rods are casting #3418645 which I guess are 74-80 360, 76-86 318. Six of those rods are the gray steel color.

There is one of the #3418645 connecting rods that is a bronze color (all the other rods are a gray steel color). Anybody have a guess why the color difference? Thank you.

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It was undersized and they sprayed metal to make it in tolerance....
 
Seen it a lot. Far as I know that's just how some of them came through.
 
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.
 
The above is interesting. It could also be a color coding from a remanufacturer. Someone tried to sell me a set of a several different colors that were reman'd..... badly as it turns out, so NO SALE!
 
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I found some in my Mystery 360 (408) I like a matched set myself.
 
Mike, you're a connecting rod racist. lol
 
If you find a copper colored rod in your engine, you can go for a tour of the Willie Wonka factory....
 
Tony's spot on... My first Mopar involvement,was a PAW parts supplied 340... Ate a pushrod,on one of those damn intake manifold cooling trays... Knew the guy,that built the engine(on a budget). Upon teardown,6 of the 8 rods were copper dipped. The owner of the car was younger than I, said they had been doing it for years...(His old man ,ran a Max Wedge powered 61-2 Lancer for years at Famaso..The man was a crazy driver.(still remember the bumps on my forehead,from doing 100plus in the Pismo dunes in a Chevy powered rail,lol...)
 
70aarcuda said:
It was undersized and they sprayed metal to make it in tolerance....
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Wrong. Copper is way soft and would not hold up to the beating of a rod journal or piston pin can dish out. Copper is the material but it was done merely for corrosion resistance. I have seen engines with all of the rods copper coloured. The bean counters surely put a stop to it. J.Rob
 
JoeSBP said:
looks like it was stretched from hard engine braking, or maybe bent then beaten straight again!!
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The machine shop said that it was not damaged. Just a casting defect that should have been rejected. Both end holes were parallel still. No hammer marks on it.

I will not be running it again!
 
68gtxman said:
The machine shop said that it was not damaged. Just a casting defect that should have been rejected. Both end holes were parallel still. No hammer marks on it.

I will not be running it again!
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When the rod line gets short on parts, they raid the scrap bin to send anything to the engine line to keep from shutting it down...

I seen it happen.... I used to catch them at it periodically....
 
RAMM said:
Wrong. Copper is way soft and would not hold up to the beating of a rod journal or piston pin can dish out. Copper is the material but it was done merely for corrosion resistance. I have seen engines with all of the rods copper coloured. The bean counters surely put a stop to it. J.Rob
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It will hold up just fine in either end of the rod, but seems to be done mostly to tighten the small end. Since the pin is a press fit in there, the copper is effectively a shim and will work just fine in such an application.

Copper corrodes just as bad if not worse than cast iron, so it wouldn't have done diddly for 'corrosion resistance'.
 
dibbons said:
The hodgepodge 340 I am working on has one 340 connecting rod casting #2899496 which I guess was used on 68-73 340 which is the normal gray steel colro. The other seven connecting rods are casting #3418645 which I guess are 74-80 360, 76-86 318. Six of those rods are the gray steel color.

There is one of the #3418645 connecting rods that is a bronze color (all the other rods are a gray steel color). Anybody have a guess why the color difference? Thank you.

View attachment 1714945347

View attachment 1714945348
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Notice other differences between the two pictures? Take a look at the sharp edges under the nut on the non copper colored rod. I was told that these were colored by shot blasting and the smoother edges of the copper colored rod would seem to bear that out.....
 
68gtxman said:
The machine shop said that it was not damaged. Just a casting defect that should have been rejected. Both end holes were parallel still. No hammer marks on it.

I will not be running it again!
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I've got some that look a bit 'bent' looking but are not, and I checked the parallelness and it was good, so sometimes the castings are just funky.
 
so the mystery continues.....well..if I am wrong as noted above,..apparently no own offers any other facts...LOL

 
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