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Crank Shaft Inspection

Old March 21st, 2019, 09:57 PM
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Crank Shaft Inspection

I have a big problem with the Stroker crankshaft in my engine. When rebuilding the engine the journals were turned in order to fit allow for new bearings. After one run on the engine dyno we opened up the bottom end to make sure all was well. We found metal in the oil and the number 2 bearing chewed up. When we looked closely at the crankshaft we found the issue. I have a new crank coming from the same manufacturer but I would like it checked for flaws prior to balancing and installation. Are you aware of any process that lets you know what is under the surface in case you do have to machine the journals?




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Old March 22nd, 2019, 12:45 AM
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That looks like something was dropped on that journal to me.
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Old March 22nd, 2019, 04:25 AM
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Ouch, good thing you tore it back apart instead of just installing the engine! It does look like something damaged it. Good luck.
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Old March 22nd, 2019, 08:08 AM
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Originally Posted by svnt442 View Post
That looks like something was dropped on that journal to me.
The surface of the crank has no divet as if it was hit. The outline of a crack was not visible prior to installation of the shaft. Both the engine builder and machinist did not see the crack ( or lip) on inspection. I feel that this took place on the dyno as the shaft was exposed to the 625 lb/ft of TQ and 535 HP. The lip looks to have curled up and tore the bearing up. My question is still is there any way to check the metal of a crankshaft for flaws and consistency prior to installation? I have a new crank coming from the same company and would like to feel confident that if I ever have to turn the journals that I don't find a flaw below the surface. Most of the crank manufacturers use Chinese steel with some of them also getting the machine work done there. This is why I am so concerned around the QA/QC.

Last edited by rummer; March 22nd, 2019 at 08:09 AM. Reason: Spelling
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Old March 22nd, 2019, 08:42 AM
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"Hidden" flaws would not show up in anything less than a prohibitively expensive radiography inspection. Magnaflux inspection or even dye penetrant inspection available at most good automotive machine shops can show microscopic flaws in the surface metal not normally visible to the naked eye. A simple old school ringing of the crankshaft may give a hint of a crack not visible.
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Old March 22nd, 2019, 09:21 AM
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Good luck
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Old March 22nd, 2019, 05:49 PM
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Are you talking about the small imperfection (yellow arrow) Or the larger big circular mark (red) ??
The small one looks like a casting flaw. The large circle almost looks like the crankshaft had been welded and reground. There are a lot of other scratches on that journal, what the heck are those ???

I have pretty much gotten to the point that if I have to use one of those type of cranks I send them right to my crank grinder and have him regrind them and make them under right. Very few of them are suitable for use in anything other than a stock engine the way they come from the factory


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