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what happened to the LS1 I bought - #7 piston busted

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Old 04-29-2010, 08:35 AM   #1
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Default what happened to the LS1 I bought - #7 piston busted

Hey guys, trying to figure out what happened to this engine; getting a little confused.

Bought an LS1 from a wrecked 2000 corvette with 40k miles, and I was told the engine was running just fine right before it was pulled.

Got it home, pulled the heads, and saw this:

Click the image to open in full size.

Click the image to open in full size.

Broken at the ring land, common on #7, etc (nitrous maybe???). Now all the other pistons are fine. What's confusing me though is...the cylinder wall looks fine, and the combustion chamber looks good, valves look good.

I mean with a broken piston like this, shouldn't there be some damage on the cylinder wall, or the combustion chamber/valves?? What could have happened?
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Old 04-29-2010, 08:41 AM   #2
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go get yourself a stoker kit, or a refund
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Old 04-29-2010, 08:59 AM   #3
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Mine did the exact same thing at 103,000ish miles, only on number 5. I also had a cracked block directly opposite the ring land failure (@5 o'clock position). I don't use nitrous either. Let me see if I can find the thread and pics.....

Here it is:
http://www.ls1tech.com/forums/genera...-mile-ls1.html
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Old 04-29-2010, 10:33 AM   #4
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Thanks guys. There were no shavings or broken chunks in the cylinder or anywhere. The connecting rod looked fine too. It's almost as if someone just installed a busted piston in a decent motor.

When I get a new piston/rod back from the engine shop, I'll put it in, do a compression check/leakdown test and see what the results are.

1CAM, read your thread, that sucks man, what motor did you end up going with? stroker?
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Old 04-29-2010, 03:00 PM   #5
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Yeah, it's really weird (re: suspicious) that a huge chunk of aluminum piston like that evacuated the engine and didn't leave any damage behind. 9 times out of 10, a piece gets caught in the quench area between the head and piston, and sticks into either of the surfaces. You usually find chunks in the manifold as well.

See if you can find any signs that the engine might have been rebuilt. I think that might be the more likely explanation.
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Old 04-29-2010, 03:16 PM   #6
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Thanks KCS...I might post a pic of the heads' combustion chamber when I get home. It looks fine to me but maybe I'm missing something.

The intake manifold was gone when the motor was pulled, btw...
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Old 04-29-2010, 03:24 PM   #7
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happened to mine at 37k same cyl i think it was detonation from using regular gas on my dumb part
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Old 04-29-2010, 03:39 PM   #8
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a piston cracked on me too. cost a ton of ******* money to fix.
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Old 04-29-2010, 04:03 PM   #9
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Not sure about where the missing piece of piston went, but it looks like the detonation could be caused by an oil contamination issue. Excess oil in your combustion chamber can cause detonation even in a low compression engine.
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Old 04-29-2010, 04:07 PM   #10
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Was the motor boosted? I only ask cuz thats usually the piston that fails do to it being the last one that gets the least fuel
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Old 04-29-2010, 04:13 PM   #11
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This happened to my STOCK never been opened motor, but to #5 and #7 with 58,XXX on it. I never got an explenation and why it could happen
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Old 04-29-2010, 05:48 PM   #12
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Very common, number 7 cylinder runs hot. Toss a tune in there with it and yer all set for a number 7 failure. GM stopped putting the rear water cross over on the later engines and this is the result.
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Old 04-29-2010, 08:10 PM   #13
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heres what mine looked like i had a catback only but i also ran regular gas and had the stock tune so it was my falt being young dumb and cheap
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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Old 04-29-2010, 08:42 PM   #14
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Quote:
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heres what mine looked like i had a catback only but i also ran regular gas and had the stock tune so it was my falt being young dumb and cheap.
Wow, almost the same exact spot too.
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Old 04-30-2010, 12:44 AM   #15
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The chances of a big chunk of metal finding its' way out of the cylinder through the exhaust valve without doing further damage along the way are VERY slim. Conversely, who would put a motor together with a piston that looks like that? Time to call Perry Mason on this one.
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Old 04-30-2010, 02:17 AM   #16
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does look in the same spot lol here it is when i pulled the head
Click the image to open in full size.
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Old 04-30-2010, 06:39 AM   #17
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That's kind of damage you will get when the ring end gap isn't enough. "If" that cylinder runs hotter, that could be the problem.
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Old 04-30-2010, 08:54 AM   #18
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Mine made it out of the exhaust port. There were no pieces in the oil pan, and like stated in my thread, there was not any room around the ring for pieces to get by. It is very possible for a piece to shoot out of the exhaust valve.
I ended up with an iron 6.0L block bored to 4.07" with Wiseco pistons, Eagle rods, and a Compstar 4.100" crank.
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Old 04-30-2010, 04:08 PM   #19
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Thanks for the responses guys. That is crazy that the SAME SPOT is common on this piston when it breaks. lol

SS4, what was your solution, honestly? Did you get replace the pistons/rods on #5 and #7? Or did you pull the engine and take everything to a machine shop?
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Old 04-30-2010, 04:30 PM   #20
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At least there was no other damage. My buddies LS7 had an exhaust valve heads break off in #5 an destroy the head the piston and the block.
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