Ls7 heads dropping valves
Because of heat. The exhaust valve is not doing what it was intended to do with transfering and distributing the heat within the sodium filled part. If it were doing the job it was suppose to do we wouldn't have the issue which is the excessive heat causing the guides to wear quicker then normal. Add in any HP upgrades, tunes, headers, cams ect. ect. and you have a disaster waiting to happen!
Teching In
Joined: Nov 2001
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From: Texas City, TX ,USA
So again, @katech
What clearance is high enough to cause breakage?
Many are shocked to find .0100 clearance and those people have no excessive noise.
I even saw a thread in which GM stated that you would get a check engine light if your guides were worn beyond the service limit. I laughed.
What clearance is high enough to cause breakage?
Many are shocked to find .0100 clearance and those people have no excessive noise.
I even saw a thread in which GM stated that you would get a check engine light if your guides were worn beyond the service limit. I laughed.
Because of heat. The exhaust valve is not doing what it was intended to do with transfering and distributing the heat within the sodium filled part. If it were doing the job it was suppose to do we wouldn't have the issue which is the excessive heat causing the guides to wear quicker then normal. Add in any HP upgrades, tunes, headers, cams ect. ect. and you have a disaster waiting to happen!
The current heads on there have 107k miles.
No failures from either.
TECH Resident
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Teching In
Joined: Nov 2001
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From: Texas City, TX ,USA
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I wanted to go all out with TI valves and he wouldn't even let me. Wasted money is what he told me Care to explain why I had one set of ls7 heads that lasted 107k miles then?
If its some kind of design flaw why isn't it every one?
You keep drinking the "buy this!" "Buy that!" Koolaid.
I'll stick to using the same parts that I haven't had not one issue with.
Maybe you were doing it wrong?
Care to explain why I had one set of ls7 heads that lasted 107k miles then?
If its some kind of design flaw why isn't it every one?
You keep drinking the "buy this!" "Buy that!" Koolaid.
I'll stick to using the same parts that I haven't had not one issue with.
Care to explain why I had one set of ls7 heads that lasted 107k miles then?
If its some kind of design flaw why isn't it every one?
You keep drinking the "buy this!" "Buy that!" Koolaid.
I'll stick to using the same parts that I haven't had not one issue with.
100K vehicles is probably closer to total Corvettes produced since 2006. Z06 models and Grand Sport production probably isnt even half that.
So consider a only "a few hundred cars" dropping valves is an alarming #. There not that many LS7s out there. Not considering...How many of those rack up more than a few thousand miles a year?? A lack of driving them can also hide a potential problem.
Teching In
Joined: Nov 2001
Posts: 26
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From: Texas City, TX ,USA
What is the sample size? All LS7 years?
100K vehicles is probably closer to total Corvettes produced since 2006. Z06 models and Grand Sport production probably isnt even half that.
So consider a only "a few hundred cars" dropping valves is an alarming #. There not that many LS7s out there. Not considering...How many of those rack up more than a few thousand miles a year?? A lack of driving them can also hide a potential problem.
100K vehicles is probably closer to total Corvettes produced since 2006. Z06 models and Grand Sport production probably isnt even half that.
So consider a only "a few hundred cars" dropping valves is an alarming #. There not that many LS7s out there. Not considering...How many of those rack up more than a few thousand miles a year?? A lack of driving them can also hide a potential problem.
The issue affects all years 2006-2013.
There are a couple of 2010-2011s stock with dropped valves on cf.
There are over 200 cases of guide wear measured beyond the service limit on cf.
At first it was thought tunes and mods were the issue. Since that time, many stock cars with 20k miles or less, never tracked, are showing documented excessive guide wear.
The cars don't smoke, use oil or show any other usual valve guide wear symptoms other than possibly excessive valvetrain noise. We all know that's subjective.
Last edited by jdb8805; Feb 28, 2013 at 02:45 PM.
TECH Apprentice
Joined: Jan 2002
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From: Gilbert, AZ
My z06 heads were toast at 28k miles. Valve guides were 5x the service limit. Friends car was close to that at 18k miles. Other friend dropped a valve destroying the block/crank/rods/piston at <20k. The guy who bought my stock shortblock was on motor 3 because he dropped 2 valves already. So out of 4 local cars 2 dropped valves and 2 with very severly worn guides. I would say that is more than 1% effected.
So again, @katech
What clearance is high enough to cause breakage?
Many are shocked to find .0100 clearance and those people have no excessive noise.
I even saw a thread in which GM stated that you would get a check engine light if your guides were worn beyond the service limit. I laughed.
What clearance is high enough to cause breakage?
Many are shocked to find .0100 clearance and those people have no excessive noise.
I even saw a thread in which GM stated that you would get a check engine light if your guides were worn beyond the service limit. I laughed.
There are many factors here. I can't answer that question.