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#4473141 - 07/28/17 03:18 PM 5.3 LS 300k Busted Piston
JasonC Offline


Registered: 12/06/06
Posts: 620
Loc: Lynchburg, Va
Here is a pic from a 2003 Silverado 5.3 with 300k. It broke a valve which caused it to punch a hole in the Piston and trashed the combustion chamber. This truck was bought in 2006 with only 40k and it has always used M1 5w30. I'm impressed with how clean the tops of the pistons are. The rest if the bottom end was just as clean. We believe that a clogged cat is what caused the pressure buildup and broke the valve.



Edited by JasonC (07/28/17 03:20 PM)
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#4473144 - 07/28/17 03:25 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
JC1 Online   content


Registered: 11/29/08
Posts: 2998
Loc: Oshawa, Ontario Canada
Your pic is on photobucket. They are blocking links to other websites.
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#4473145 - 07/28/17 03:26 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
AZjeff Offline


Registered: 01/14/11
Posts: 2628
Loc: PV Az
never mind


Edited by AZjeff (07/28/17 03:27 PM)
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#4473150 - 07/28/17 03:30 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
Linctex Online   content


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
Originally Posted By: JasonC
We believe that a clogged cat is what caused the pressure buildup and broke the valve.


????

I kind of doubt that. I've floated many exhaust valves due to excessively high back-pressure on turbocharged race engines, and never had a failure like THAT! ("Float" is really only about .010"-.020" off the seat, any way)

clogged converter = engine has no power or quits, not broken valves.

This was a metallurgical flaw.
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#4473172 - 07/28/17 04:09 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
HerrStig Offline


Registered: 08/24/11
Posts: 9560
Loc: Boston, MA
So check the cat. I doubt it's the cause, though, more like a bad valve.

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#4473207 - 07/28/17 05:01 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
Chris142 Offline


Registered: 06/05/03
Posts: 16807
Loc: Deplorable in apple valley, ca
Valve guides got loose and let the valve bend when it seated and it eventully broke off.
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#4473274 - 07/28/17 06:41 PM Re: 5.3 LS 300k Busted Piston [Re: Chris142]
JasonC Offline


Registered: 12/06/06
Posts: 620
Loc: Lynchburg, Va
Originally Posted By: Chris142
Valve guides got loose and let the valve bend when it seated and it eventully broke off.


Incorrect. There was nothing wrong with the guide or the valve spring. The converter was clogged.
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#4473276 - 07/28/17 06:42 PM Re: 5.3 LS 300k Busted Piston [Re: Linctex]
JasonC Offline


Registered: 12/06/06
Posts: 620
Loc: Lynchburg, Va
Originally Posted By: Linctex
Originally Posted By: JasonC
We believe that a clogged cat is what caused the pressure buildup and broke the valve.


????

I kind of doubt that. I've floated many exhaust valves due to excessively high back-pressure on turbocharged race engines, and never had a failure like THAT! ("Float" is really only about .010"-.020" off the seat, any way)

clogged converter = engine has no power or quits, not broken valves.

This was a metallurgical flaw.



The converter was clogged
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#4473277 - 07/28/17 06:43 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
JasonC Offline


Registered: 12/06/06
Posts: 620
Loc: Lynchburg, Va
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#4473389 - 07/28/17 08:52 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
tomcat27 Offline


Registered: 06/25/09
Posts: 3564
Loc: Chicago, IL
crazy! what are you gonna do with it?
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#4473407 - 07/28/17 09:13 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
dishdude Offline


Registered: 11/14/08
Posts: 8725
Loc: Phoenix
Were you redlining it when that happened?
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#4473636 - 07/29/17 06:07 AM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 18947
Loc: Sunny Florida
300k with stock parts the valve guides were definitely worn. We have raised and killed dozens of 5.3's and they rarely break. We have had many clogged cats at high miles and yet zero engine failures, even when racing them at far past factory redline.

Sorry, but I don't see a clogged exhaust breaking a valve like that...
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#4473957 - 07/29/17 02:42 PM Re: 5.3 LS 300k Busted Piston [Re: JasonC]
DoubleWasp Offline


Registered: 05/21/12
Posts: 5236
Loc: Fort Lauderdale, FL
I dealt with a clogged cat on my Navigator. It was clogged so bad that I had to disable overdrive and floor the truck to get to 55 mph. Even that never broke a valve.

I suppose anything is possible, but I have much much doubt that a clogged cat was your issue.

I'm betting it was one of the other top causes of valve fracture.
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#4475437 - 07/31/17 10:39 AM Re: 5.3 LS 300k Busted Piston [Re: tomcat27]
JasonC Offline


Registered: 12/06/06
Posts: 620
Loc: Lynchburg, Va
Originally Posted By: tomcat27
crazy! what are you gonna do with it?
We put some JB Weld on the Piston and slapped it back together. Should be good for another 300k. J/K we have a crate motor going back in.
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