Burnt piston need advice - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Hcd3ss · 01-30-2020, 07:55 PM

Hey guys. I have an L99 that’s had an agpTT kit on it since 2014. So after 80k miles it started knocking some. I thought it was an afm lifter and started disassembly to fully delete afm parts, only to find the rear most driver side piston has melted (or perhaps broken off ‘then completely vaporized’) a small chunk right at the squish band.. so I’m currently building the short block as there was no damage to anything but the piston. Anyway, what has me concerned is that I haven’t located what caused this.. i know that I had low octane gas in the tank when this happened.. but could that cause the cylinder to cook like that? Also, isn’t it strange that the spark plug from that cylinder still had the complete ground strap intact? I was thinking if it were from some detonation I would have heard it, felt it, and it would show on the plugs.. there is no damage to the heads, no damage to the bore of the block, it looks like someone just chipped off a corner of the piston and made it disappear.. the ONLY indication that I have of there being any loose metal or anything inside they cylinder is that the electrode of the spark plus was bent off center (where it didn’t sit directly under the ground strap anymore). But this is bothering me. I don’t want to put this motor back together to have it fail again because I’ve overlooked something..
p.s. I just sent the injectors to get flow tested and cleaned. So that is already done.. any other suggestions or insight would be greatly appreciated.

olblue75 · 01-30-2020, 08:26 PM

It probably blew out the exhaust valve.

Hcd3ss · 01-30-2020, 08:31 PM

Yeah, but it’s not in the manifold, and it didn’t go thru the turbo. Not to mention that this is quite a substantial piece to have any chance of making it thru the exhaust valve.. the piece missing is roughly the size of the last 2 digits of your pinky finger.. tho it would be substantially thinner.. I can’t convince myself that it could have made it thru the valve, then cleanly thru the turbine of the turbo. That seems impossible to me.

Greenhornet2 · 01-30-2020, 09:35 PM

I've seen it make it through the valve no problem it probably broke into multiple pieces especially if they were stock pistons, they can kinda shatter. Making it through the turbo with no damage a little harder to believe. Check out the intake too pieces can make it back through the intake valve too.

Hcd3ss · 01-30-2020, 10:44 PM

Any ideas on what may have caused this damage on only one cylinder?

InFiD3ViL · 01-31-2020, 12:17 AM

Did you show a picture of this a few weeks ago?

I remember someone showing damage just like this where you could see the missing crown chunk of the piston above the top ring land, but there was no damage at all to the face of the piston from pieces flying around. Nor was there any visible damage to the chamber under the head.

Greenhornet2 · 01-31-2020, 06:53 AM

Could have been a little lean got too hot detonation approaching power level limits of the stock pistons? It doesn't seem like you were pushing it if you got 80k on a TT what kinda power are you putting out? What were you doing when it started knocking?

GONIF · 01-31-2020, 10:33 AM

Hypereutectic pistons are not as forgiving as forged . I am sure you already know that ,In a FI engine forged pistons are your best bet. Why in the hell was low octane fuel in your tank ? Sounds like the low octane fuel was your problem. You were ready at 80000 miles for a freshen up anyway. I see a set of Wiseco pistons in your future .

Hcd3ss · 01-31-2020, 12:28 PM

No I didn’t post any pictures of this. Haven’t even taken any actually, and yeah definitely a set of forged pistons.

CamaroBarb · 01-31-2020, 12:45 PM

Quote:

Originally Posted by Hcd3ss

Hey guys. I have an L99 that’s had an agpTT kit on it since 2014. So after 80k miles it started knocking some. I thought it was an afm lifter and started disassembly to fully delete afm parts, only to find the rear most driver side piston has melted (or perhaps broken off ‘then completely vaporized’) a small chunk right at the squish band.. so I’m currently building the short block as there was no damage to anything but the piston. Anyway, what has me concerned is that I haven’t located what caused this.. i know that I had low octane gas in the tank when this happened.. but could that cause the cylinder to cook like that? Also, isn’t it strange that the spark plug from that cylinder still had the complete ground strap intact? I was thinking if it were from some detonation I would have heard it, felt it, and it would show on the plugs.. there is no damage to the heads, no damage to the bore of the block, it looks like someone just chipped off a corner of the piston and made it disappear.. the ONLY indication that I have of there being any loose metal or anything inside they cylinder is that the electrode of the spark plus was bent off center (where it didn’t sit directly under the ground strap anymore). But this is bothering me. I don’t want to put this motor back together to have it fail again because I’ve overlooked something..
p.s. I just sent the injectors to get flow tested and cleaned. So that is already done.. any other suggestions or insight would be greatly appreciated.

Its very possible you lifted a ring land. If it were mine I clearance the top ring at least .010 more than they call for running TT's. The rings get a little too hot over expand and pop the edge of the piston off. From there is just a matter of time before the piston fails. Very common believe it or not. I've seen it over and over especially on boosted stock bottom ends. the thread posted a few weeks ago was same thing but he wasn't boosted. Stuff happen's. Also that number 7 cylinder runs a little leaner than the others. Always put your highest flowing injector in that hole.

Greenhornet2 · 01-31-2020, 02:04 PM

87 octane and boost don't mix.

Boother · 01-31-2020, 02:11 PM

Quote:

Originally Posted by CamaroBarb

Its very possible you lifted a ring land. If it were mine I clearance the top ring at least .010 more than they call for running TT's. The rings get a little too hot over expand and pop the edge of the piston off. From there is just a matter of time before the piston fails. Very common believe it or not. I've seen it over and over especially on boosted stock bottom ends. the thread posted a few weeks ago was same thing but he wasn't boosted. Stuff happen's. Also that number 7 cylinder runs a little leaner than the others. Always put your highest flowing injector in that hole.

This^

InFiD3ViL · 01-31-2020, 02:21 PM

Quote:

Originally Posted by Hcd3ss

No I didn’t post any pictures of this. Haven’t even taken any actually, and yeah definitely a set of forged pistons.

Ok. I am trying to find that post/user. They had similar damage to this with no traces of the broken piston chunk. It seemed like way to big a piece to just disappear.

LsxDoctor · 01-31-2020, 02:23 PM

Quote:

Originally Posted by CamaroBarb

Its very possible you lifted a ring land. If it were mine I clearance the top ring at least .010 more than they call for running TT's. The rings get a little too hot over expand and pop the edge of the piston off. From there is just a matter of time before the piston fails. Very common believe it or not. I've seen it over and over especially on boosted stock bottom ends. the thread posted a few weeks ago was same thing but he wasn't boosted. Stuff happen's. Also that number 7 cylinder runs a little leaner than the others. Always put your highest flowing injector in that hole.

Agreed. Seen this happen many many times on sbe FI LS motors.

01-30-2020, 07:55 PM	#1
Hcd3ss Drives: 2011 camaro 2ss/RS Join Date: Nov 2013 Location: Waycross, Ga Posts: 80	Burnt piston need advice Hey guys. I have an L99 that’s had an agpTT kit on it since 2014. So after 80k miles it started knocking some. I thought it was an afm lifter and started disassembly to fully delete afm parts, only to find the rear most driver side piston has melted (or perhaps broken off ‘then completely vaporized’) a small chunk right at the squish band.. so I’m currently building the short block as there was no damage to anything but the piston. Anyway, what has me concerned is that I haven’t located what caused this.. i know that I had low octane gas in the tank when this happened.. but could that cause the cylinder to cook like that? Also, isn’t it strange that the spark plug from that cylinder still had the complete ground strap intact? I was thinking if it were from some detonation I would have heard it, felt it, and it would show on the plugs.. there is no damage to the heads, no damage to the bore of the block, it looks like someone just chipped off a corner of the piston and made it disappear.. the ONLY indication that I have of there being any loose metal or anything inside they cylinder is that the electrode of the spark plus was bent off center (where it didn’t sit directly under the ground strap anymore). But this is bothering me. I don’t want to put this motor back together to have it fail again because I’ve overlooked something.. p.s. I just sent the injectors to get flow tested and cleaned. So that is already done.. any other suggestions or insight would be greatly appreciated.

01-30-2020, 08:26 PM	#2
olblue75 Drives: 2010 2SS/RS Join Date: Dec 2009 Location: Clarksville Tennesse. Posts: 6,064	It probably blew out the exhaust valve. __________________ Orange Krush II 1LE Front sway bar, Splitter, shocks and struts, Z28 dual mode mufflers, Intake, UCA Bushings, and Toresen 3.91 Diff. 1 piece DSS Drive Shaft, ZL1/C7 Calipers, and 32mm JPSS Rear Bar. ASC race spec splitter and wicker. 6th Gen M017 Wheels. Stainless Works 1 7/8 LTs. DSE and PAFDT Suspension components.

01-30-2020, 09:35 PM	#4
Greenhornet2 Drives: 2011 Camaro 2SS LS3 Whipple Join Date: May 2019 Location: Connecticut Posts: 1,925	I've seen it make it through the valve no problem it probably broke into multiple pieces especially if they were stock pistons, they can kinda shatter. Making it through the turbo with no damage a little harder to believe. Check out the intake too pieces can make it back through the intake valve too. __________________ Whipple 2.9 CAI ID1050x injectors ZL1 Pump JRE FPCM JMS Voltage booster JRE Rough Idle blower cam BTR .660 springs CHE trunnion kit 1 7/8 Speed Engineering Borla Atak JRE scoop 1.5" lowering springs BMR trailing arms and toe links Cradle inserts 704WHP 603WTQ 93 octane

01-31-2020, 12:17 AM	#6
InFiD3ViL Drives: 2010 CGM 2SS/RS LS3 Swapped A6 Join Date: Sep 2016 Location: Spring Hill, FL Posts: 4,575	Did you show a picture of this a few weeks ago? I remember someone showing damage just like this where you could see the missing crown chunk of the piston above the top ring land, but there was no damage at all to the face of the piston from pieces flying around. Nor was there any visible damage to the chamber under the head. __________________ 2010 CGM Camaro 2SS LS3 Swapped A6 - GPI LS3 SS1 .647/.638, (224/237, 112 +4, 7º overlap) on CamMotion 8620 core, BTR Platinum .660" Dual Spring kit w/titanium retainers, CHE bronze trunnion upgrade, stock heads milled @ .015, Melling HV 10296 oil pump, TSP 1-7/8" long tube headers (W/Catless Off-road Pipes), Corsa Xtreme 3" Catback, GPI Ported/Rod Mod Intake, Stage 2 Ported Throttle Body, Vararam OTR CAI, Mike Norris Gen 2 catch can + GM 1LE clean side separator, 160º thermostat - Megan Racing adjustable coilovers (lowered 1.75"), MRR M017 10/11" wheels-Tuned by Ryan @ GPI

01-31-2020, 06:53 AM	#7
Greenhornet2 Drives: 2011 Camaro 2SS LS3 Whipple Join Date: May 2019 Location: Connecticut Posts: 1,925	Could have been a little lean got too hot detonation approaching power level limits of the stock pistons? It doesn't seem like you were pushing it if you got 80k on a TT what kinda power are you putting out? What were you doing when it started knocking? __________________ Whipple 2.9 CAI ID1050x injectors ZL1 Pump JRE FPCM JMS Voltage booster JRE Rough Idle blower cam BTR .660 springs CHE trunnion kit 1 7/8 Speed Engineering Borla Atak JRE scoop 1.5" lowering springs BMR trailing arms and toe links Cradle inserts 704WHP 603WTQ 93 octane

01-30-2020, 08:31 PM	#3
Hcd3ss Drives: 2011 camaro 2ss/RS Join Date: Nov 2013 Location: Waycross, Ga Posts: 80	Yeah, but it’s not in the manifold, and it didn’t go thru the turbo. Not to mention that this is quite a substantial piece to have any chance of making it thru the exhaust valve.. the piece missing is roughly the size of the last 2 digits of your pinky finger.. tho it would be substantially thinner.. I can’t convince myself that it could have made it thru the valve, then cleanly thru the turbine of the turbo. That seems impossible to me.

01-30-2020, 10:44 PM	#5
Hcd3ss Drives: 2011 camaro 2ss/RS Join Date: Nov 2013 Location: Waycross, Ga Posts: 80	Any ideas on what may have caused this damage on only one cylinder?

01-31-2020, 10:33 AM	#8
GONIF Drives: 73 VETTE ,, 05 2500hd diesel,14 1LE Join Date: Feb 2014 Location: The Left lane PHOENIX AZ Posts: 2,626	Hypereutectic pistons are not as forgiving as forged . I am sure you already know that ,In a FI engine forged pistons are your best bet. Why in the hell was low octane fuel in your tank ? Sounds like the low octane fuel was your problem. You were ready at 80000 miles for a freshen up anyway. I see a set of Wiseco pistons in your future . __________________ OLD GUY FLYING FAST AND LOW Last edited by GONIF; 01-31-2020 at 10:44 AM.

01-31-2020, 12:28 PM	#9
Hcd3ss Drives: 2011 camaro 2ss/RS Join Date: Nov 2013 Location: Waycross, Ga Posts: 80	No I didn’t post any pictures of this. Haven’t even taken any actually, and yeah definitely a set of forged pistons.

01-31-2020, 02:04 PM	#11
Greenhornet2 Drives: 2011 Camaro 2SS LS3 Whipple Join Date: May 2019 Location: Connecticut Posts: 1,925	87 octane and boost don't mix. __________________ Whipple 2.9 CAI ID1050x injectors ZL1 Pump JRE FPCM JMS Voltage booster JRE Rough Idle blower cam BTR .660 springs CHE trunnion kit 1 7/8 Speed Engineering Borla Atak JRE scoop 1.5" lowering springs BMR trailing arms and toe links Cradle inserts 704WHP 603WTQ 93 octane