[Z06] Took GM to court over dropped valve, and....
06-22-2011, 10:44 AM
#22
Race Director
Can't say it surprises me to read a LS-7 fragged, apparently due to bad valve guides. Have read several instances just like yours (minus the legal brouhaha).
What surpises me is how Chevrolet's "independent" PE could so woefully misdiagnose what seems so obvious to even an untrained eye. And while I've nothing but respect for PEs of any discipline? Know all-too-well what one has to achieve in order to attain a 'PE' rating & the stamp? I'm now really wondering exactly WTH this PE saw justifying his report? That guy needs to retake the PE exam.
In any event glad you'll be getting a new LS-7, even if it took going to the matt with GM.
What surpises me is how Chevrolet's "independent" PE could so woefully misdiagnose what seems so obvious to even an untrained eye. And while I've nothing but respect for PEs of any discipline? Know all-too-well what one has to achieve in order to attain a 'PE' rating & the stamp? I'm now really wondering exactly WTH this PE saw justifying his report? That guy needs to retake the PE exam.
In any event glad you'll be getting a new LS-7, even if it took going to the matt with GM.
06-22-2011, 10:50 AM
#23
Racer
Another important abnormality observed is the exhaust valve rocker tip. The tip is grounded during manufacturing to provide a profiled contact surface to the lash pad. Instead of grounding the full width of the tip, the sloping side of the rocker tip is not grounded. Hence, a step exists just adjacent to the grounded surface.
[IMG]
[/IMG]One would think that if everything is designed and manufactured properly, the lash pad would not make contact with this “step”. As the following photos clearly show, part of the “step” is shinny and contact did take place with the lash pad.
[IMG]
[/IMG][IMG]
[/IMG]My estimate is there was an overlap of approximately 0.015” between the edge of the lash pad and the step. Of all the eight exhaust rockers, six of them have a step that is approximately 10 thou tall. One is about 5 thou and there is one that is almost flat (the right one in the photo below).
[IMG]
[/IMG]With the step, it will induce a torsional load into the rocker which is resisted by the two needle roller bearings at the ends of the trunnion. All of the intake rockers, in contrast, have the full width of their tips grounded (since it has no offset sloping side) and wear pattern on the tip is perfectly normal.
06-22-2011, 10:59 AM
#24
Pro
I am so glad to see somebody winning a warrantee case. I am not smart enough yet to fully understand the valve issue in detail. But glad to see you forcing the car company to honor the warrantee.
Back 100 years ago, I had an Eagle Talon TSI burst into flames (from under the hood) and Chrysler denied my warrantee. I had to make it an insurance claim and got stuck deep underwater on the loan. I will never spend another penny with Chrysler.
Maybe GM raises the price of the warrantee to accomodate what they see as more claims than expected. Fine with me. Just stay in the customer's corner. Service and quality are the only hopes we have for manufacturing in this country.
Back 100 years ago, I had an Eagle Talon TSI burst into flames (from under the hood) and Chrysler denied my warrantee. I had to make it an insurance claim and got stuck deep underwater on the loan. I will never spend another penny with Chrysler.
Maybe GM raises the price of the warrantee to accomodate what they see as more claims than expected. Fine with me. Just stay in the customer's corner. Service and quality are the only hopes we have for manufacturing in this country.
06-22-2011, 11:30 AM
#26
Race Director
I'm no lawyer, but settling probably just applies to this one case, and doesn't set any precedent for any problems that anyone else may have.
There's no court finding concerning the problem, so if anybody else brings up the problem, each case will have to go through this same lengthy process to fight for what should be a general finding that automatically applies to all of LS7 engines.
I'm glad the OP got a satisfactory resolution, but it probably doesn't do the rest of us much good - we'll all have to fight the battle individually every time this problem pops up in another engine.
Bob
2006 Z06
06-22-2011, 11:59 AM
#27
Drifting
Member Since: Nov 2009
Location: Murrells Inlet, SC (formally New Windsor, NY)
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I'm thinking the same. One would think the valve guide wear would leave specific metallic particles behind in the oil. I'm going to send mine out for analysis next time I change it.
06-22-2011, 12:10 PM
#29
Very good write up and analysis. I could read good research like this all day long. A question:
Are you certain that the rocker tips are ground prior to installation? Could the smoothing noted be from wear and not preinstallation finishing? The step/ridge would then be an artifact of the wear left on the tip from operation.
Also, and a comment here, I've been amazed from the beginning how many people have been awed by the whole "hand building" "promotion".
It's never been claimed that parts used in the "hand building" are individually inspected by the "builder" or anyone else. The parts used in the LS7 apparently are just "out of the bin" parts with no additional inspection or attempt to match them to one another in a particular engine.
If the rocker tips are ground prior to installation and the step was present at installation it would seem that MINIMAL attention on the part of the "builder" aka "assembler" would have detected the aberration.
Apparently this situation was never noticed by any of the "builders". This doesn't change my opinion about the value of the so called "hand assembled" engine. However, I think it should be considered by those who are boosters of this feature of the LS7-a feature that has been sold as having tangible worth.
Are you certain that the rocker tips are ground prior to installation? Could the smoothing noted be from wear and not preinstallation finishing? The step/ridge would then be an artifact of the wear left on the tip from operation.
Also, and a comment here, I've been amazed from the beginning how many people have been awed by the whole "hand building" "promotion".
It's never been claimed that parts used in the "hand building" are individually inspected by the "builder" or anyone else. The parts used in the LS7 apparently are just "out of the bin" parts with no additional inspection or attempt to match them to one another in a particular engine.
If the rocker tips are ground prior to installation and the step was present at installation it would seem that MINIMAL attention on the part of the "builder" aka "assembler" would have detected the aberration.
Apparently this situation was never noticed by any of the "builders". This doesn't change my opinion about the value of the so called "hand assembled" engine. However, I think it should be considered by those who are boosters of this feature of the LS7-a feature that has been sold as having tangible worth.
06-22-2011, 12:15 PM
#30
Sorry to hear about the hassle it took to get them to warranty it. It's pretty sad they fought this hard to not fix a $75k vehicle.
06-22-2011, 12:15 PM
#31
Le Mans Master
06-22-2011, 12:50 PM
#33
Race Director
They settled because it's cheaper than going to trial and they don't want to set a precedent for future potential claims. It's all about the bottom line. Nothing surprising here.
I am not taking sides, that is just my .02.
I am not taking sides, that is just my .02.
06-22-2011, 01:03 PM
#34
I read the same thing. Yeah, but GM settled!!!
I'm no lawyer, but settling probably just applies to this one case, and doesn't set any precedent for any problems that anyone else may have.
There's no court finding concerning the problem, so if anybody else brings up the problem, each case will have to go through this same lengthy process to fight for what should be a general finding that automatically applies to all of LS7 engines.
I'm glad the OP got a satisfactory resolution, but it probably doesn't do the rest of us much good - we'll all have to fight the battle individually every time this problem pops up in another engine.
Bob
2006 Z06
I'm no lawyer, but settling probably just applies to this one case, and doesn't set any precedent for any problems that anyone else may have.
There's no court finding concerning the problem, so if anybody else brings up the problem, each case will have to go through this same lengthy process to fight for what should be a general finding that automatically applies to all of LS7 engines.
I'm glad the OP got a satisfactory resolution, but it probably doesn't do the rest of us much good - we'll all have to fight the battle individually every time this problem pops up in another engine.
Bob
2006 Z06
From what I am able to gather, seems like you're right.Settling doesn't mean that they are admitting to any wrongdoing, or fault.
He mentions in his prior thread that he was planning on using the small claims court system in his area which he stated has a maximum claim of $20,000.
When you figure that the MSRP on an LS7 is around 14K for us, and less than that for GM, then it made more sense for them to settle than to drag it out. Defending themselves, might end up costing them more. It's a little like totaling a car. Once you reach a repair estimate approaching a given percentage of the value of the car, it makes more sense for the insurance company to just total it.
Also, I have seen where usually a settlement includes an agreement not to discuss the case or the terms of the settlement, so it will be interesting to see just what the original poster can and does say in the second part of his post.
06-22-2011, 01:23 PM
#36
Melting Slicks
hoefi, I am sorry you had to endure such pain to get your engine replaced. I appreciate you taking the time to post so the rest of us can learn from it.
My theory is these failures are the result of several contributing factors. The LS7 is a relatively recent design, but the valve train is very similar to the current Big Block Chevrolet (BBC) aftermarket cylinder heads. The BBC started out in 1965 with a 26 degree valve angle and has evolved into aftermarket 12 degree valve angle cylinder heads. This is very similar to the LS7 12 degree valve angle design. To decrease the valve angle, the cylinder heads are tipped up on the intake side to straighten the airflow path (this increases volumetric efficiency) but the result is increased valve stem side loading. Several other contributing factors have evolved such as elimination of lead in gasoline (lead is an excellent lubricant), reduction of zinc ZDDP in the oil (ZDDP is also an excellent high pressure lubricant), and the push for leaner mixtures with the resulting higher temperatures. We would not even consider building a current BBC 12 degree race engine with anything less than bronze valve guides and one piece quality valves (titanium or stainless). We also would not build one with hypereutectic (cast) pistons. Combine inexpensive two piece exhaust valves with cheap integral steel guides and cast pistons and the eventual results are catastrophic.
As we consider modifying our LS7 engines, we should learn from others and replace the 2-piece exhaust valves, cast pistons, and the integral steel valve guides.
My theory is these failures are the result of several contributing factors. The LS7 is a relatively recent design, but the valve train is very similar to the current Big Block Chevrolet (BBC) aftermarket cylinder heads. The BBC started out in 1965 with a 26 degree valve angle and has evolved into aftermarket 12 degree valve angle cylinder heads. This is very similar to the LS7 12 degree valve angle design. To decrease the valve angle, the cylinder heads are tipped up on the intake side to straighten the airflow path (this increases volumetric efficiency) but the result is increased valve stem side loading. Several other contributing factors have evolved such as elimination of lead in gasoline (lead is an excellent lubricant), reduction of zinc ZDDP in the oil (ZDDP is also an excellent high pressure lubricant), and the push for leaner mixtures with the resulting higher temperatures. We would not even consider building a current BBC 12 degree race engine with anything less than bronze valve guides and one piece quality valves (titanium or stainless). We also would not build one with hypereutectic (cast) pistons. Combine inexpensive two piece exhaust valves with cheap integral steel guides and cast pistons and the eventual results are catastrophic.
As we consider modifying our LS7 engines, we should learn from others and replace the 2-piece exhaust valves, cast pistons, and the integral steel valve guides.
06-22-2011, 01:24 PM
#37
Drifting
Member Since: Nov 2009
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The tolerances in in high horsepower engines needs to be tighter and more precise than the run of the mill production 'sports car" engine. The OP definitely makes a good case here with PLENTY of evidence showing the tolerances of the valve guides grew rapidly to the point of creating a valve failure. I think he is correct in his assessment of how the engine failed. And I believe he is also correct that the breakdown is premature and due to faulty maunufacturing.
I am still not one of "the sky is falling" supporters. I do believe that the LS7 is a good engine. I think that the quality control of some parts is the culprit in the engine issues(rocker bearing, valve guides,oil pan leaks).
Thankfully I have had no problems with my Z. My LS7 runs flawlessly and I hope it always will. I am grateful the OP has shared his information with us. The valve failure issue is a hot topic. Maybe this info will give us all some insight in preventing it form ever occurring in our cars.
I am still not one of "the sky is falling" supporters. I do believe that the LS7 is a good engine. I think that the quality control of some parts is the culprit in the engine issues(rocker bearing, valve guides,oil pan leaks).
Thankfully I have had no problems with my Z. My LS7 runs flawlessly and I hope it always will. I am grateful the OP has shared his information with us. The valve failure issue is a hot topic. Maybe this info will give us all some insight in preventing it form ever occurring in our cars.
06-22-2011, 01:55 PM
#38
The Consigliere
Member Since: May 2006
Location: 2023 Z06 & 2010 ZR1
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OP,
Thanks for posting. We need to get this valve guide issue figured out.
Thanks for posting. We need to get this valve guide issue figured out.
06-22-2011, 02:23 PM
#39
Melting Slicks
Great write up! Thanks for posting. Glad you won!
I think Vito.A has some very valid info. I have the same " To Do List " after my warranty runs out.
OP: Would you post what brand motor oil you have been using?
Do you guys think a good set of roller rockers would take some loading away from the valve/Stem?
I think Vito.A has some very valid info. I have the same " To Do List " after my warranty runs out.
OP: Would you post what brand motor oil you have been using?
Do you guys think a good set of roller rockers would take some loading away from the valve/Stem?
06-22-2011, 02:28 PM
#40
Race Director
The tolerances in in high horsepower engines needs to be tighter and more precise than the run of the mill production 'sports car" engine. The OP definitely makes a good case here with PLENTY of evidence showing the tolerances of the valve guides grew rapidly to the point of creating a valve failure. I think he is correct in his assessment of how the engine failed. And I believe he is also correct that the breakdown is premature and due to faulty maunufacturing.
I am still not one of "the sky is falling" supporters. I do believe that the LS7 is a good engine. I think that the quality control of some parts is the culprit in the engine issues(rocker bearing, valve guides,oil pan leaks).
Thankfully I have had no problems with my Z. My LS7 runs flawlessly and I hope it always will. I am grateful the OP has shared his information with us. The valve failure issue is a hot topic. Maybe this info will give us all some insight in preventing it form ever occurring in our cars.
I am still not one of "the sky is falling" supporters. I do believe that the LS7 is a good engine. I think that the quality control of some parts is the culprit in the engine issues(rocker bearing, valve guides,oil pan leaks).
Thankfully I have had no problems with my Z. My LS7 runs flawlessly and I hope it always will. I am grateful the OP has shared his information with us. The valve failure issue is a hot topic. Maybe this info will give us all some insight in preventing it form ever occurring in our cars.