Exploded piston after 400 miles please help

[rjack]

First off thank you for any help and taking time look this over. i have a 2010 camaro with a l99 we converted to ls3 we also added cold air, long tubes and phastech stage 3 cam, ported/polished heads and completely redone rotating assembly (.030) the engine builder told me all he could find was the truck pistons which were almost identical to the car pistons so i went with it. this is my first time tuning although i am a master tech with solid engine knowledge its uncharted water for me so i am naturally cautious/scared. we installed the engine and i put the attached tune into the vcm (followed Tuning School Procedure) the engine sounded good and was strong, we drove the car 400 miles and i was doing the first oil change and decided to tweak the tune ,All I Did Was Change The idle timing from 20 to 22 at idle and the engine would barley start (had to hit gas pedal) instantly i heard some knock so i loaded the original tune back (attached) and started it up. the knocking got real bad real quick so i turned off the engine and bore scoped all cylinders to find the #2 piston completely missing the ring stuck in a valve and sleeve cracked, i haven't disassembled it yet but looks like the piston grenaded. i know i had good oil pressure and at most the fuel trims were + 10 At Idle (both banks) with a afr of roughly 15 @ idle maybe 16 tops (WB on Opposite Bank ) there was little to no KR but im wondering if the pinging from the long tubes was distorting it. any way wondering if a more experienced tuner can look at this and let me know if there is something completely off to warrant the piston explosion to be my fault. THANKS

[GHuggins]

Hate to be the one to sound bad here, but for starters you would definitely get more help on the gen 4 section. Secondly, lot of work done to be adding timing without fixing the fuel tables for the motor. What was the wot air fuel ratio? Cam alone can really lean one out in areas, but your also bored and have better flowing heads to boot... Neither the VE or Maf tables have been touched. PE still also nearly stock and wasn't modified like some will do to hit wot fuel goals. In fact not a whole lot at all was changed for the extra fuel demands. If the intake tube was original it could have possibly kept you close off of maf alone, but you still running a combo setup up to stock rpm settings for dynamic fueling and I still would like to know what the wot air fuel was? Could have just been piston failure. Could have been very lean and cracked or melted the piston from overheat? Hard to tell from tune alone...

[rjack]

You Dont Sound Bad And Thank You. WOT PE Was 12 to 13.7. With The Trims And AFR In The Ball Park I Felt Like It Was Ok Until I Got A Little Break In Time On The Engine. The Tunning School Method Of Tuning The Maf And VE Tables is A Little Extream I Felt For A Fresh Build, Evan The Part Throttle Tunning Has You @ 4000 In Second Gear (Maybe Im Wrong). My Intent Was To Finish The Tune @ First Oil Change When It Blew On Me. I Thought It Was Kinda Crazy AFR LTFT Being Decent With Almost Stock Tune Too Then Somthing Like This Happens And I Question Everything. Again Thanks And Sorry For Posting In Wrong Forum I Didn't Realize

[GHuggins]

I'de still be interested in knowing what the piston looked like. Whether it was part failure or tune failure. Even 13.7 being on the lean side, it's not that bad especially when you think about all of the stock trucks out there running 14.7 wot from the factory even though they do run a lot less timing... Good tunes can run lean and still be ok... Guess It would depend on how rough it was driven for break-in? Parts definitely aren't what they used to be. Especially performance stuff...

[rjack]

Unfortunately This Is What It Looks Like.
I Dissembled it today and the piston was disintegrated! Those two chunks in the picture are the largest i could find.
In the picture looking into the cylinder you cant really see it but the piston went right through the cast sleeve and aluminum block, ring stuck in valve and rod bent/twisted, The circlip for the wrist pin was perfectly intact at the bottom of pan so im assuming it fell of and the piston got tweaked and went through the wall but it went back t the machine shop so well see what the official verdict is tomorrow.
Thank You Thank You THANK YOU!! For looking over that tune and giving me piece of mind, im sure you're busy,
image1.jpgimage1 3.jpgimage2.jpg

[schpenxel]

Got a copy of a log??

I agree with Ghuggins.. seems very little was done to that tune.

MAF table wasn't touched
Virtual VE data wasn't touched
Looks like a good bit of timing was added
Knock recovery was increased by 60x (!!!)
Base retard was cut in half or more (!!!)
Fuel injector data wasn't touched
PE ratio wasn't touched
Idle adapt spark table were brought down way, way low

I'd have to see a log before I'd believe the AFR was really that close on this tune. Knock probably killed it given how fast it was putting timing back in after it saw knock..

[Redline MS]

I'de still be interested in knowing what the piston looked like. Whether it was part failure or tune failure. Even 13.7 being on the lean side, it's not that bad especially when you think about all of the stock trucks out there running 14.7 wot from the factory even though they do run a lot less timing... Good tunes can run lean and still be ok... Guess It would depend on how rough it was driven for break-in? Parts definitely aren't what they used to be. Especially performance stuff...

Agreed.....it may not make power but it shouldn't blow up...usually the heat will melt something vs breaking something...knock on the other hand is like a bull dozer in a china shop. Also keep in mind shit breaks!

If we really think about it....its absolutely amazing that these stock engines take the pounding they do. We push them far past what GM had really designed the parts.....when you finally break it...its a sad moment but its our greed for power that has to be considered.

[GHuggins]

Agreed.....it may not make power but it shouldn't blow up...usually the heat will melt something vs breaking something...knock on the other hand is like a bull dozer in a china shop. Also keep in mind shit breaks!

If we really think about it....its absolutely amazing that these stock engines take the pounding they do. We push them far past what GM had really designed the parts.....when you finally break it...its a sad moment but its our greed for power that has to be considered.

I thankfully haven't blown one yet, but as long as it's on a dyno the power numbers via ignition hook test usually will keep you in the "OK area", then common sense on air fuel from there... Did unfortunately lift the heads on one about 2 months ago getting over zealous, working too much with very little sleep and screwing up a scaled tune Luckily it was our test mule and not a customers... That would have been a very bad day... Plus other than needing the top of the engine disassembled again, no damage done... Did feel like a jackhole though...

The fact that the OP mentioned the engine builder could only find truck pistons made me wonder if this "built" motor had OE pistons... They fail in OE engines on their own much less a built motor? Spark knock could have definitely killed it... It is what lifted the heads on ours after all

[cesar]

seems knock killed the piston.

[sunny]

Looking at the top of the piston right next to it and the matching combustion chamber on the head IMHO it wasn't tune related.

[schpenxel]

Based on...?

[GHuggins]

No signs of knock. However it does appear leanish... AND just because there's no signs of knock on one piston doesn't necessarily mean there wasn't some in another cylinder... Also saw no signs of melting around the edges of the break like it had been run too lean... Wondering if the engine had the right diameter pistons or was blueprinted at all and possibly started the whole scenario by breaking a piece of piston skirt off via piston slap? Seen plenty of new pistons the wrong diameters straight out of the box This would also explain the quick engine death...

[JnJSpdShop]

Unfortunately This Is What It Looks Like.
I Dissembled it today and the piston was disintegrated! Those two chunks in the picture are the largest i could find.
In the picture looking into the cylinder you cant really see it but the piston went right through the cast sleeve and aluminum block, ring stuck in valve and rod bent/twisted, The circlip for the wrist pin was perfectly intact at the bottom of pan so im assuming it fell of and the piston got tweaked and went through the wall but it went back t the machine shop so well see what the official verdict is tomorrow.
Thank You Thank You THANK YOU!! For looking over that tune and giving me piece of mind, im sure you're busy,

Is it just me or do the liners look real thin? What was the bore on this engine?

[GHuggins]

First pic = lots of air gap around the second piston too... Doesn't seem very "performance built" to me... Going back to my previous question in wondering if the engine was blueprinted and what the piston clearances were? Might just be me, but I'm still leaning towards that... Spark knock could have still made things worse though by rocking or causing the piston to kick in it's bore forcing a skirt to break off... Lots of unknowns here

[gmonde]

I am not a tuning pro by any means and actually learning hp tuners ,, but have built plenty of engines , worked with carbs, intakes ,old school tuning, I have seen leaned out damage, nitrous damage ,parts failure, detonation ,,, if the detonation is bad enough it will take out the ring lands down to the rings and loose compression and cylinder pressure and that would be the extent the piston would stay intact (9 time out of ten) and as you explained you where not under wot, if lean to the point of burning it look like sand blast hit the edges of the piston ,from the picture I don't see that ,, I see the wrist pin off to one side makes me think clip wasn't all the way in the groove and slid out causing the piston to get stuck in the bore (as you suspected) ,,, we had distributors locked with no timing advance @36 degrees running on the edge of 93 octane pump gas and nothing like this ,,, check the piston to wall clearance on the other pistons just to be sure there wasn't a mistake was made on the piston size ,, I hate to see stuff like this but it happens ,,,, always double check your work or shops work ,, hopefully your vendor will step up if they assembled it ,, good luck with getting back running

[Ben Charles]

I just read this... I highly doubt it was the tune

[10_SS]

I held my 1985 S-10 2.5 Iron duke to the floor in neutral and it revved at some crazy high rpm for about 3 seconds... then it shattered a piston exactly like this, just from over-rev. The rod+pin were bouncing around the cyl the same as what's in this pic... it's the loudest rod knock you will ever hear. So I would say weak piston casting, or overrev. Or there was a slight over-rev that caused the weak piston to fail. Pull all the pieces of the piston and try to look for a void (inconsistency) in the casting along the cracks.. I split a 2005 Dodge Ram front center section wide open, the split started at the pinion bearing... I thought I did it, but my wife of all people looked along the cracked alum and noticed there was excessive porosity right at the pinion bearing race... that creates a weak spot, and it cracked wide open due to that. She worked at a few suspension suppliers as a supplier quality engineer, and 90% of the time if they have alum parts that fail, it's due to excessive porosity.

[rjack]

Ive Attached A Log File Of A Part To Mid Throttle Run About A Week Before The Piston Explosion, The Bore Was .030 I Just Got The Short Block Back From The Rebuildes At No Charge So Im Assuming There Taking Responsibility. GMONDE You Are Quite Observant As That is what several others have said abut the wrist pin being off center. The pistons and bore where checked by the builder the first time and now again after new block and bore, this time he told me the pistons he reused for the new block where shrunk .001 from the first time he assembled the original engine (possibly from knock?) so i am concerned about this tune. ive also learned the stock tune i downloaded from the vcm was a hypertech tuner tune that i think throughs off the tuning school process for tuning? Thank You All Very Much for youre responses and help!

[10_SS]

you didn't have floating pins? I assumed you did. My builder always suggests floating pins on any build.