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Discussion Starter #1
I lost compression in my 1999 cobra a while back and finally got it torn apart to find a broken ring land. The second ring land down on the number seven cylinder. What could cause this?
 

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King Trashmouth
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Do you have a better closeup of the affected area? Are those rings intact? What does the bore look like?

Given the top ringland looks intact that rules out detonation and AFR. It doesn't look completely scuffed so it may not be overheating. That leaves it down to insufficient ring gap, improper assembly, insufficient material/design, or the toughest of all, inter-ring pressure.
 

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Discussion Starter #3
It ran for 20k miles being run pretty hard in that time shifting North of 7k. But i drove 700 miles each way two years ago on a road trip. I assembled the motor myself and set all clearances for light boost because at the time that was my goal.
 

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Discussion Starter #4
The cylinder was scored where the piston was broken, and the top ring us intact but the bottom was not. The oil ring seems to be intact as well.
 

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King Trashmouth
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It's always tough to look at a couple pictures and tell, but between the look of bending on the broken ringlands rather than a clean shear, and the scoring on the bore, I'd strongly lean toward insufficient 2nd ring gap leading to ring butting and ringland failure in this case. Did you gap the rings yourself, and if so did you record the values?
 

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Discussion Starter #6
I did gap them myself and record the values but I can't seem to find them right now. I know i gapped them big to accept boost. From what I've seen, it's possible that because the drivers head I have is one with the cooling issues, it caused that cylinder to overheat. maybe that caused the ring to expand too much?
 

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King Trashmouth
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I would be skeptical of overheating as a root cause. Usually if it's overheat both sides of the piston are scuffed to hell. I see a little scuffing on that one, but nothing outrageous. When they overheat it looks like someone smeared aluminum all over the bore too, and even then I've rarely seen a ringland failure with that. If cylinders 6 and 8 look pretty scuffed/melted too it might lend some credence, but short of that I'd be skeptical.

This link here has a good picture of what a scuffed/overheated piston looks like:
AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - When Is An Engine Overheated And Why, Part-II
 

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who done the tuning? what brand of rings?
 

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Discussion Starter #9
Street Lethal performance did the tuning and the rings were sealed power stainless I believe.
 
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