View Full Version : what happened to the LS1 I bought - #7 piston busted


demonpixel
04-29-2010, 09:35 AM
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:

http://sites.google.com/site/zigzautonotes/images/broken_piston1.jpg

http://sites.google.com/site/zigzautonotes/images/broken_piston2.jpg

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? :confused:

trans_am7935
04-29-2010, 09:41 AM
go get yourself a stoker kit, or a refund

1CAMWNDR
04-29-2010, 09:59 AM
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/generation-iii-internal-engine/1038760-not-merry-christmas-103-000-mile-ls1.html

demonpixel
04-29-2010, 11:33 AM
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?

KCS
04-29-2010, 04:00 PM
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.

demonpixel
04-29-2010, 04:16 PM
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...

therobman
04-29-2010, 04:24 PM
happened to mine at 37k same cyl i think it was detonation from using regular gas on my dumb part

ULTIMATEORANGESS
04-29-2010, 04:39 PM
a piston cracked on me too. cost a ton of fucking money to fix.

TT632
04-29-2010, 05:03 PM
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.

youngrigo
04-29-2010, 05:07 PM
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

SS4Luck
04-29-2010, 05:13 PM
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

HotSilverBird
04-29-2010, 06:48 PM
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.

therobman
04-29-2010, 09:10 PM
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
http://i16.tinypic.com/8b9o12q.jpg
http://i11.tinypic.com/6ns51s7.jpg
http://i6.tinypic.com/7xnlq45.jpg

KCS
04-29-2010, 09:42 PM
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.

eallanboggs
04-30-2010, 01:44 AM
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.

therobman
04-30-2010, 03:17 AM
does look in the same spot lol here it is when i pulled the head
http://i8.tinypic.com/4t736s6.jpg

Auto Concepts
04-30-2010, 07:39 AM
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.

1CAMWNDR
04-30-2010, 09:54 AM
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:devil:.

demonpixel
04-30-2010, 05:08 PM
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?

rich5368
04-30-2010, 05:30 PM
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.

youguessit
04-30-2010, 07:09 PM
when my motor did that it didnt burn oil but fuel got into the oil... was wierd. till i pulled the heads off i mean. Did it in 7. sam shit only on the very top of piston. didnt hurt the heads. Detonated off....

RENE'S RAGE
04-30-2010, 07:25 PM
The piston probally broke off alittle at a time, as to one big chunk.
Shot out the exhaust, in small peices.

demonpixel
05-02-2010, 02:44 AM
The piston probally broke off alittle at a time, as to one big chunk.
Shot out the exhaust, in small peices.

Maybe so....still...I've heard stories of people dropping a small nut down an intake manifold and have it wreak havoc everywhere. :bomb:

RENE'S RAGE
05-02-2010, 10:51 AM
Maybe so....still...I've heard stories of people dropping a small nut down an intake manifold and have it wreak havoc everywhere. :bomb:

Oh yeah, I was just saying maybe that's why you didn't find a large chunk of piston anywhere and no other damage.

66 BADBOY
05-02-2010, 01:26 PM
I don't wanna sound like a moron, but would this type of damage show up if a compression test was done on a motor? Just curious because I picked up a 60K mile 2001 LS1/A4 the other day. Compression checks were all around 185-195.

I'm wondering if its a good idea just to pull the heads to be sure? Or should I not worry about it because of the compression tests results?

demonpixel
05-02-2010, 02:16 PM
I don't wanna sound like a moron, but would this type of damage show up if a compression test was done on a motor? Just curious because I picked up a 60K mile 2001 LS1/A4 the other day. Compression checks were all around 185-195.

I'm wondering if its a good idea just to pull the heads to be sure? Or should I not worry about it because of the compression tests results?

I don't think it would show up as much, because there's not an explosion going off. Combustion is not happening; the piston is just moving up and down.

Now, people will tell you that it's always a good idea to tear down a junkyard/used motor, and no one will tell you that you should pull a junkyard motor and run it in whatever car you want to put it in.

No one will ever tell you that, BUT people do it, and it turns out fine. Having said that, you don't know if anyone's run nitrous through a junkyard/used motor, or ran low octane gas when they should have run higher octane gas, etc.

It takes a little time (and money since you have to get new head bolts) to pull the heads on a used motor, but it's never a BAD idea to do so.

I'm glad I pulled the heads on mine man. A broken piston sucks, but it could have been way worse. I just put the oil rings and piston rings on the new piston and the machine shop already hung the piston on the rod, so I'm about to clean the deck surface and the head surface and put in the new piston.

I think the broken piston piece DID go out the intake, because there are some weird scratches around the cathedral port. Nothing that would cause sealing issues with the intake manifold; it just doesn't look normal.

KCS
05-02-2010, 02:22 PM
The piston probally broke off alittle at a time, as to one big chunk.
Shot out the exhaust, in small peices.

If it's a bunch of pieces, then the chances should be better that at least one of them would have been left behind, or at least leave evidence, like a marking or something. To have them all leave out of the exhaust valve all nice and neat just doesn't seem likely. Not to mention, it would have to travel across the cylinder to reach the exhaust valve, when the intake valve and quench pad are right above it.

KCS
05-02-2010, 02:23 PM
I don't wanna sound like a moron, but would this type of damage show up if a compression test was done on a motor? Just curious because I picked up a 60K mile 2001 LS1/A4 the other day. Compression checks were all around 185-195.

I'm wondering if its a good idea just to pull the heads to be sure? Or should I not worry about it because of the compression tests results?

I don't know about a compression test, but possibly a leakdown test.

peedeerooster
05-02-2010, 09:37 PM
I have a 2005 CTSV. I had installed a Fast 92mm, NW 90mm ported TB, TFS 215cc heads, headers and all the usual boltons. The car was around 480 rwhp on the stock longblock. The AFR was in the 12.7 range and timing was 24 degress. After about 20,000 miles with the head, cam and intake, the engine started burning oil and smoking. Tore the engine down and you could move the #7 piston around in the bore with your thumbs. All other cylinders were tight and in good shape. I didn't have anything broken like the piston or rings. It just looked worn out. The shortblock was factory and only had 46,000 miles on it. Just put in a forged 408 shortblock. Will see what happens now.

Chalky
05-03-2010, 02:02 PM
Same thing happened to my old 02 Z. 11.5:1 CR, tuned. Broke off in same place.

Pulled the piston and wrist pin was almost frozen solid, piston woudl just barely rock on wrist pin.

demonpixel
05-03-2010, 08:37 PM
Well guys, I got a new piston and went to go install it today. Can't believe I didn't notice this before, but check this out, looks f'd up:

http://sites.google.com/site/zigzautonotes/images/broken_piston_cylinder1.jpg

http://sites.google.com/site/zigzautonotes/images/broken_piston_cylinder2.jpg

This is the #7 cylinder bore. I have no idea if that's fixable or not. Ran my finger over it and you can definitely feel a change in surface. Not comfortable putting that piston in now. :bang: :bang:

So now I'm trying to think of what options I have. So far I've come up with these options:

1. Tear everything down, take it to a machine shop, see if they can repair it and if so, pay the $$ and put everything back together.

2. Tear everything down, find a good stock block that's got good 8 cylinders, and swap everything over to it.

3. Start completely over with a new LS engine.

4. Give up and sell everything.

I feel like total shit right now because it feels like I'm basically one cylinder away from having a good daily driver muscle car. :cry:

Anyone else have any other options? Thanks guys, I appreciate the advice.

KCS
05-03-2010, 09:37 PM
That looks like a crack, but it might just be some crud on the cylinder wall. Take it to a machine shop and they can bump it in the hone very lightly and see whether it's cracked or not. You may get lucky...then again, nothing else has really gone right with this thing.

demonpixel
05-06-2010, 09:34 AM
Hmmm...would a flex hone help before taking it to the machine shop (I've never flex honed before)? One of these:

http://home.roadrunner.com/~gstowell/hone2007.jpg

I heard flex honing doesn't change the bore diameter, so I should still be able to use the stock piston/rings, correct?

KCS
05-06-2010, 11:53 AM
Maybe not. In a rigid hone, like at a machine shop, if it's cracked it would leave a shadow where the stones didn't touch. A flex hone is designed to conform to whatever shape the bore is in, so you won't get that same effect. It'll just clean up the cylinder, but that's what the rigid hone is going to do anyways.

redz_02
05-07-2010, 12:54 PM
Can't you overbore the cylinders .05? Would that clean it up?

I thought a flex hone is just to polish/debur the cylinder walls.

demonpixel
05-07-2010, 03:20 PM
Can't you overbore the cylinders .05? Would that clean it up?

I thought a flex hone is just to polish/debur the cylinder walls.

If I bore it 0.050 over, and get a new piston for it, I'm not sure how bad that would throw off the balancing of the rotating assembly.

KCS can probably confirm this.

KCS
05-07-2010, 04:52 PM
Can't you overbore the cylinders .05? Would that clean it up?

I thought a flex hone is just to polish/debur the cylinder walls.

Not .05", but you can hone it .005". If the sleeve is cracked, it's typically all the way through and sometimes the aluminum behind it is cracked as well. It's repairable, just probably not worth it on an LS1 block.

Flex Hones can restore surface finishes on a cylinder wall for a new set of rings to seat. It's not going to change the bore geometry, or remove enough material to use a larger piston, but it can be used just to get a nice new surface finish for a rebuild.

Also, yeah a .005" over piston probably will throw off the balance a considerable amount. Not necessarily because it's a larger piston, but the material is different and can be heavier itself.

demonpixel
05-11-2010, 11:03 AM
Block is junk because of the crack. :bang: :bang:

The hunt is on for a new block...

sjsingle1
05-11-2010, 01:28 PM
so still no clues as to why this happens to so many engines????

demonpixel
05-11-2010, 03:09 PM
I was told that it's because of the intake manifold design. #7 is the last to get air, the air is denser, and this creates a lean condition. Increase the heat a little, or clog your #7 injector a little, and your #7 piston goes :bomb: at the ringland.

NemeSS
05-11-2010, 04:59 PM
I was told that it's because of the intake manifold design. #7 is the last to get air, the air is denser, and this creates a lean condition. Increase the heat a little, or clog your #7 injector a little, and your #7 piston goes :bomb: at the ringland.

maybe if the tune is incorrect.
ive built psi ls motors even with c5 intake manifolds and have never had a ring land come apart on me to date in any ls motor. spun bearings.once
maybe some people just have bad luck

demonpixel
05-11-2010, 05:34 PM
Maybe, but this happens waaaay too much on these motors.

KCS
05-11-2010, 06:44 PM
maybe if the tune is incorrect.
ive built psi ls motors even with c5 intake manifolds and have never had a ring land come apart on me to date in any ls motor. spun bearings.once
maybe some people just have bad luck

By "psi ls motors", do you mean super/turbocharged engines? In that case, I don't think you would see this very often since the intent is to create manifold pressure, which would seem to be more likely to equalize pressure in the plenum better. On NA and nitrous engines, where I think this is most common, I would expect that you would get a ramming effect in the back of the manifold creating a denser air charge (re: leaner) for that #7 runner.

NemeSS
05-12-2010, 01:34 PM
By "psi ls motors", do you mean super/turbocharged engines? In that case, I don't think you would see this very often since the intent is to create manifold pressure, which would seem to be more likely to equalize pressure in the plenum better. On NA and nitrous engines, where I think this is most common, I would expect that you would get a ramming effect in the back of the manifold creating a denser air charge (re: leaner) for that #7 runner.

yes, used the sealed ls1 c5 intake few times. and even the fbod intakes with a brass plug in the egr bore.

KCS
05-19-2010, 06:01 PM
So what's the update? Did this guy ever compensate you for any of it?

SOMbitch
08-10-2010, 09:40 PM
Back from the dead....... My #7 looked EXACTLY like the OP pic!!! SAME spot EVERYTHING!!! IDENTICAL spot!!! I only have phone pics so I will take some with the camera later and post up. Car threw no codes and ran fine but it may not have run long since this happened...

I just wanna know so the new 403 going in doesn't suffer the same fate...

CraZee ZO6
12-02-2010, 08:29 AM
back from the dead again.. my # 7 cracked piston looked the same.. on motor too h/c setup. PTV was good and all... valve hit the piston and plug tip was bent!

sucks cheap fix is still $ and u leave with same hp.. so I went the long route... expensive fix but u leave with a shit load of power! hahaha
6 bolt head 427 in the works for me. now if that breaks ill jump a cliff..

Z06 Steve
12-02-2010, 08:40 AM
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.
my guess is the seller took the heads off to inspect then removed the chunk and buttoned it back up put it up for sale!:bang:

KCS
12-02-2010, 10:21 AM
Since Zig (demonpixel) is on vacation, I'll go ahead and post an update for him.

The old block was indeed cracked so it was junk. We found a new LS6 block, rebuilt it with a Wiseco/Lunati spec piston, and just before he went left on vacation, he heard it his old 'Bird fire up for the first time in months. Pardon the mess. The next step is to clean it all up and get rid of the rat's nest. BTW, that's EFI on there...

http://i15.photobucket.com/albums/a353/KShrake/DSCF4686.jpg

http://i15.photobucket.com/albums/a353/KShrake/DSCF4691.jpg

http://i15.photobucket.com/albums/a353/KShrake/CIMG0268.jpg

http://i15.photobucket.com/albums/a353/KShrake/CIMG0270.jpg

http://i15.photobucket.com/albums/a353/KShrake/DSCF4723.jpg

LS1MCSS
12-02-2010, 10:52 AM
You say that's EFI. Is that the Professional Products self tuning EFI? If so, how good does it work?

KCS
12-02-2010, 11:12 AM
You say that's EFI. Is that the Professional Products self tuning EFI? If so, how good does it work?

I'm pretty sure it's the BOSS EFI (http://www.autoworksracing.com/boss_efi_throttle_bodies_and_acc.htm) system. On the LS1, it's basically only been fired up and driven into the garage, so I can't really say for sure how well it works yet, but it worked very well when he had it on the old Pontiac 400 that was in there.

ShevrolayZ28
12-02-2010, 01:59 PM
love the old Formula!

Ya, it sucks when this happens. My H/C car had a similar failure at 38kmi. It knocked/clacked quite noticeably afterward (I doubt the OPs motor ran quietly with that broken ring land). Upon disassembly, there was little evident damage, only a slightly bent spark plug ground electrode, some light colored speckling on the combustion chamber, and a piece missing off the #7 ring land.:barf:

I thought maybe the broken piece was fired cleanly out the exhaust port, but once I got the oil pan off and removed the steel baffle, I found a good amount of finely ground aluminum.

I have no idea why it failed. The car was tuned by someone that knows their stuff. I may have gotten some bad gas or had weak fuel pressure.

A million dollars later, I have a nice stroker in it now, and I'll be looking for low tens come Springtime :D

CraZee ZO6
12-02-2010, 04:09 PM
shev...shit happens mine was tuned by Carmen from vette doctors. stock piston ringlands can take so much...well not much. Especially if your hard on the car and enjoy it.

well onto bigger and better things.

Intercooler2
12-02-2010, 04:15 PM
We documented a zz4. Same crap and found ring gaps too tight