Strange Failure

[Fingers]

I have a customer that has managed to break a piston, but not in a way I am familiar with. The cracks are between the pin and the crown, but do not extend into either. They do not show on the underside either. The is some discoloration of the metal, but not conclusive of overheating. Very strange.

A quick run through the Thermal Analysis on the computer says that a loss of oil cooling could create a ring stress issue. That is, the center is hot and expanding while the outside is cool and contracted. But there is no clear evidence that oil cooling was lost or inadequate.

I am going to use some die penetrate on the cracks before I dissect the piston so I can see the extent/depth of the cracks.

I am told these pistons have seen several seasons and I am told some 900 or more passes at 1000 HP. I don't know the compression at this time.

 

[dirty_max]

I think I saw a pic of it, you must be a magician to analyze that thing :roflmao:. sounds like it stood through a pretty good test of time though.

 

[malibu795]

Subd

 

[jlawles2]

Can't see the picture. Do the cracks run perpendicular to the top of the piston or radially around the rim?

Could it be scratchs? Could it just be a bad casting?

 

[Fingers]

I think I saw a pic of it, you must be a magician to analyze that thing :roflmao:. sounds like it stood through a pretty good test of time though.

Well, I do have the software and a very good model of the piston. To do a complete job takes a lot more work. But it does provide insight.

 

[malibu795]

I know Heather powels truck hank ate one... She posted up on Facebook yesterday....someone else manage to kill some?

 

[Fingers]

I'm still looking into Heather's. I'll know more when I get the piston in my hands. It is very beat up. My initial thoughts are something hit the piston because the broken off piece is no where near a stress/weak point.

To answer Adam's question: There are others that have broken because of problems outside of the piston itself. Dropped valves, broken turbos, failed rings, and piston-head clearance issues. The one with the strange crack at the beginning of this thread is the only one that I think might actually be the piston at this time.

I don't post other people's carnage pictures/stories unless they either want me to or have already been posting them themselves.

I will post about any pistons that fail because of the piston. Thus, this thread, because I think there is a chance it is the piston that failed.

 

[RickDLance]

I will post about any pistons that fail because of the piston. Thus, this thread, because I think there is a chance it is the piston that failed.

This is what makes this guy who he is.:thumb:

 

[malibu795]

I don't post other people's carnage pictures/stories unless they either want me to or have already been posting them themselves.

I will post about any pistons that fail because of the piston. Thus, this thread, because I think there is a chance it is the piston that failed.

No problems here with that approach :thumb:

 

[Fingers]

I was so focused on the location of the crack that I didn't look so closely at the crown. The valves had been hitting this piston, and its brethren.



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[Fingers]

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[JoshH]

Is that from the valve contacting the piston or the piston contacting the head?

 

[Fingers]

It is the valve contacting the piston. That is the valve pocket in the picture

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[JoshH]

Valve pocket as in reliefs for an aftermarket cam?

 

[Yellow Jacket]

So you are saying there wasn't enough valve clearance factored in at build time or something changed over time, correct?

 

[S Phinney]

It is the valve contacting the piston. That is the valve pocket in the picture

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How deep are your pockets on those Jon? How hard did they turn this engine if you know?

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[Fingers]

I have to back off on the valves hitting. On close examination, I see they are marks from the machining process. The process has improved so much that I forgot what the early pistons looked like.

My bad.

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[Fingers]

Another picture:




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[JoshH]

That's pretty wild looking.

 

[Chevy1925]

That's pretty wild looking.

x2!