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Just checking I’m not going mad! 400/4 conrod shells.

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Deano400:
Just taken the conrods off the crank to check the condition of the shells and was surprised to see three of the pairs of shells had Black markings. The reason I was surprised is the conrods are marked with a 1. I was expecting conrods marked 1 to have either Red, Yellow or Green shells.

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I used plastigage to check the clearance which looks ok.

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The forth conrod was clearly Green shells with a 3 on the conrod so appears fine.

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Everything seems fine just confused with the Black markings on the shells. No visible markings on the crank to help me.
So I suppose my question is, could they be red shells that have gone black with age and heat? Bearing in mind the Green shells are clearly Green.
Any thoughts and experience would be appreciated.

Oddjob:
It's quite common practice to use black shells instead of the correct colour. Reasons can be, the correct colour wasn't available, reds are hard to find for instance. Or the owner couldn't work out the correct colour for himself for some reason. The trick of reading the letter and number codes wasn't commonly known until a few years ago unless you were in the trade.

If you use black shells, which are the thickest shell, all you need to do is run them in very carefully and they'll wear to the correct thickness over time.

Trigger:
The table is for new parts. It is only good if you are using a new crank and rods and not for second hand parts which is worn  ;)
Looks to me like it has been measured up by an engineer and shells fitted for the correct clearances.

Deano400:
Thanks Ken and Graham.
The more I look I'm pretty sure they are Black and not discoloured. The fact that the plastigage looks good I think what you are saying Graham is probably the case. Thanks again.

Trigger:

--- Quote from: Deano400 on March 11, 2022, 11:54:32 AM ---Thanks Ken and Graham.
The more I look I'm pretty sure they are Black and not discoloured. The fact that the plastigage looks good I think what you are saying Graham is probably the case. Thanks again.

--- End quote ---

Without seeing it up close and personal, i would say it has been re-shelled before.

I have had so many members engines here over the years that they have rebuilt by the owner with advice on shell codes from other members on the forum that always point to the chart in the workshop manual and it has made a mess of there crank. If the plastigage is good, then that is the correct measurement  ;)

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