copper plated connecting rod? - Team Camaro Tech
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post #1 of 13 (permalink) Old Aug 23rd, 08, 06:55 PM Thread Starter
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copper plated connecting rod?

I have never seen anything like this after working with the Chevy V-8 for over 45 years. I am doing an engine rebuild on a friends 62 Corvette 327 300 horse. During the teardown I noticed something odd about one of the connecting rods. Upon removal and clean-up of the piston and rod I could clearly see that the big end of the rod, including the cap, was copper plated. The plating goes half way up the rod "I" beam. Has anyone ever seen something like this before? Could this be a way of adding weight to a light rod? Any old timers have any ideas?
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post #2 of 13 (permalink) Old Aug 23rd, 08, 07:08 PM
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Re: copper plated connecting rod?

I have a set that is copper plated on the small end. I assumed it was done by a rebuilder to add material to the bore as a salvage technique so that the pin would fit tightly. Why the big end Don't know.

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post #3 of 13 (permalink) Old Aug 23rd, 08, 07:52 PM Thread Starter
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Re: copper plated connecting rod?

The mystery deepens!!
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post #4 of 13 (permalink) Old Aug 24th, 08, 08:38 AM
 
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Re: copper plated connecting rod?

No mystery, if you have ever worked in the motorcycle industry. A friend of mine has, for years, and what is done with the copper is done to localize heat treatment levels.

"Motorcycle full circle rods don't have any parting lines in them on their big ends, and use roller bearings, no bolted on caps. The rod would need a different heat treat on the load surfaces on either end, bearing hardness, and a completely different 'softer' hardness treat for the beam section. The copper draws heat away from the base metal it is clad to, and the treat is lower than unclad metal areas. So, the rod gets treated bearing hardness on the inner race ends, and a completely different hardness for the beam and outer ends. Bearing hardness treat for the beams would make the beam much more brittle, and subject to cracking/failure/breakage. I understand new rods in selected automotive engines, especially General Motors U.S. manufactured engines, go through this dual, or multiple heat treat process, especially if they are cast, and some forged performance rods get it too, to assist in the stability of the bolt boss, and other areas of those rods."

Hope this helps.

Regards,

Milton
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post #5 of 13 (permalink) Old Aug 24th, 08, 11:05 AM Thread Starter
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Re: copper plated connecting rod?

I can see this being done on all 8 rods ,but why only on one? I believe it is meant as a type of repair procedure.
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post #6 of 13 (permalink) Old Aug 24th, 08, 11:55 AM
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Re: copper plated connecting rod?

I suspect, as you said, it may have been done to reduce the diameter of the bore just a little bit.

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post #7 of 13 (permalink) Old Aug 24th, 08, 01:59 PM
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Re: copper plated connecting rod?

Bill,
Very common practice from the oem's. 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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post #8 of 13 (permalink) Old Aug 24th, 08, 07:57 PM
 
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Re: copper plated connecting rod?

So, this copper coating is done to the rod BORES? Doesn't make any sense if so, all the factory has to do to refinish a rod big end is to cut the bolt pads and re-hone the big ends, and doing that to a small end doesn't sound like the way to do it for a pressed pin rod.

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Milton
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post #9 of 13 (permalink) Old Aug 25th, 08, 05:45 PM
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Re: copper plated connecting rod?

Quote:
Originally Posted by The Devil's advocate View Post
So, this copper coating is done to the rod BORES? Doesn't make any sense if so, all the factory has to do to refinish a rod big end is to cut the bolt pads and re-hone the big ends, and doing that to a small end doesn't sound like the way to do it for a pressed pin rod.

Regards,

Milton
Milton,
You have to remember that the factory rods are done on automated equipment, I doubt that there is a cap grinder anywhere in the area.

I have probably seen at least a hundred of them over the years and they work just fine. Dont forget, these are production engines, not race stuff. Most of them will never see 3000 rpm in thier entire lives.

You would be absolutely amazed at how bad the factory machining tolerances are, especially on the older engines. Cranks vary all over the place, rods the same. I have seen 440 Chrysler rods that varied 40 grams, thats right 40 come out of a perfectly good running engine with 150k miles on it. I have a 400 Small Block in the shop right now that has been completely machined and when we went to put the cam bearings in, one hole is .005" smaller than it is supposed to be I have the cam bearing up in the lathe to cut it in the morning.

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post #10 of 13 (permalink) Old Aug 25th, 08, 07:37 PM
 
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Re: copper plated connecting rod?

I realize production tolerances are usually all over the place, but CNC stuff should be consistent, either bad, or good. Seems bad is the order of the day. Only thing I would question the GM folks is, copper, vs bronze? Copper is dead soft, bronze is a lot more resilient. I know this because one of my grandfathers, was a copper miner in Brigham, Utah in the early years, and I mean early years, of the 20th century. I'd have chosen bronze.

As far as my friend's info goes, it is right on for copper clad full circle, roller bearing rods for motorcycles, and they just don't have much wear in their hardened bearing bores, from what I have seen.

Thanks for the info, Bill, I didn't know that those rods were that bad they need repair when they are new. That is the great thing about learning something new every day.

Regards,

Milton
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post #11 of 13 (permalink) Old Aug 26th, 08, 06:27 PM
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Re: copper plated connecting rod?

Milton,
I would actually have to say it is an alloy of some type. It has a red tint to it compared to pure copper.

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post #12 of 13 (permalink) Old Aug 26th, 08, 07:32 PM Thread Starter
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Re: copper plated connecting rod?

my single plated rod is definitely an alloy or pure copper. There is one spot on the side of the rod where the plating is beginning to peel off. It is very thin and extremely sharp?
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post #13 of 13 (permalink) Old Aug 27th, 08, 11:33 AM
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Re: copper plated connecting rod?

Flint and Tonawanda built engines at 300 per hour (one every 12 seconds), and they were amazingly reliable back in the day, in spite of the machining technology they had to work with. You should have seen them stuff pistons/rods - it'd scare you to death!
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