[Z06] Root Cause for Excessive Guide Wear Found
01-05-2013, 04:31 PM
#1821
Regarding the top part of your response-
I didn't say GM only knows "the score in part"- I said that may be the case. You don't know, nor do I. Any further discussion becomes purely speculative.
Regarding GM's statement about a machining error in the valve guide and your related question "What other details would it be helpful to know?"-
That's easy. How about identifying whether it was guides bored to the wrong diameter, or installed off line laterally from the valve seat, or installed off angle in the other axis? This would make it much easier for us to determine if our particular motor has the problem, rather than relying on somebody like John to start from scratch and attempt to figure it out for all Z06 owners.
I didn't say GM only knows "the score in part"- I said that may be the case. You don't know, nor do I. Any further discussion becomes purely speculative.
Regarding GM's statement about a machining error in the valve guide and your related question "What other details would it be helpful to know?"-
That's easy. How about identifying whether it was guides bored to the wrong diameter, or installed off line laterally from the valve seat, or installed off angle in the other axis? This would make it much easier for us to determine if our particular motor has the problem, rather than relying on somebody like John to start from scratch and attempt to figure it out for all Z06 owners.
You said:
Let me make sure I follow you Les. You're saying that they might have fixed it, and they might not have.
And either way, we have no way of knowing because they have not given us enough to go on.
If we are conceding that we have "no way of knowing" well then what is the point in continuing to look????
And either way, we have no way of knowing because they have not given us enough to go on.
If we are conceding that we have "no way of knowing" well then what is the point in continuing to look????
Or more to the point, if one finds out they have according to the techniques described in this discussion, "bad geometry."
I am curious.
What do they then do? What is the plan? And who in here has implemented it? What kinds of results have they gotten, and under what circumstances?
People have been observing, and effectively dealing with the valve matter for years now.
Experts in their fields, many of them.
Perhaps I am looking at it with well, a jaundiced eye. But I tend to look at what we are seeing here, as well, reinventing the wheel.
I showed my own examples of my own heads. With shot exhaust guides in them.
Out of curiosity, what do you make of all of this?
Many years ago I worked with a very close friend- overall, a good guy. He just lived to argue. He thrived on it and would argue to the death over the most minute points if needed because he needed to prevail in the end. Unfortunately, this tendency put him in conflict with too many people and too many policies over time. His career suffered tremendously as a result and he lost sight of the things that were really important. I mention him, not because what happened to him is pertinent to you,
I'm a little bit different in that regard to which you refer to yourself, because for many of us, time is of the essence.
I recall my first of several conversations with John Armstrong (Ranger), back when we started the initial C6 Z06 Fast List. He had taken a lot of heat from those who didn't particularly care for him or his methods.
Didn't like his driving tips, wanted him to release his data logs, etc.
One day, he told me, "Ricky, all I want is for people to get the most out of their cars."
That, has stuck with me.
As such, my greatest concern, is with those who do not have the luxury to merely discuss this matter, and discuss theories, but with those who actually have to do something about it, aside from "talking" about it.
Not those like yourself, whom I cannot for the life of me, see how they not only arrive at, but are convinced that there are supposedly "causes" aside from those already, if not outright known and discussed, then certainly show compelling evidence that they are at the root of this issue, and convinced even further, that GM and Katech are "hiding something" in an attempt to "thwart" those "investigating" it and trying to get at "the truth".
My goal is to help those who are asking "What do I need to do to protect myself from this issue, right now?"
The options out there for managing it, are out there from Katech, and others.
Others who have a proven track record of managing it.
The most important thing is, that those options have proven to be effective, over time, and under extreme use.
This cannot be argued with.
People in the position of warranties running out, those ready to modify their cars, those planning on regularly tracking their cars such as Howie and others, those people have to take action, as opposed to anything else.
That is my point of view on this whole subject, and why, when I look at Jason's comment, I can understand fully what he meant by it.
Last edited by '06 Quicksilver Z06; 01-06-2013 at 02:24 AM.
01-05-2013, 04:37 PM
#1822
Race Director
I can respect your perspective. Out of curiosity, how many LS7s do you believe this discussion, and it's fruits, have saved?
Or more to the point, if one finds out they have according to the techniques described in this discussion, "bad geometry."
I am curious.
What do they then do? What is the plan? And who in here has implemented it? What kinds of results have they gotten, and under what circumstances?
People have been observing, and effectively dealing with the valve matter for years now.
Experts in their fields, many of them.
Perhaps I am looking at it with well, a jaundiced eye. But I tend to look at what we are seeing here, as well, reinventing the wheel.
I showed my own examples of my own heads. With shot exhaust guides in them.
Out of curiosity, what do you make of all of this?
I appreciate that. Because it's not.
I'm a little bit different in that regard.
I recall my first of several conversations with John Armstrong (Ranger), back when we started the initial C6 Z06 Fast List. He had taken a lot of heat from those who didn't particularly care for him or his methods.
Didn't like his driving tips, wanted him to release his data logs, etc.
One day, he told me, "Ricky, all I want is for people to get the most out of their cars."
That, has stuck with me.
As such, my greatest concern, is with those who do not have the luxury to merely discuss this matter, and discuss theories, but with those who actually have to do something about it, aside from "talking" about it.
Not those like yourself, whom I cannot for the life of me, see how they not only arrive at, but are convinced that there are supposedly "causes" aside from those already, if not outright known and discussed, then certainly show compelling evidence that they are at the root of this issue, and convinced even further, that GM and Katech are "hiding something" in an attempt to "thwart" those "investigating" it and trying to get at "the truth".
My goal is to help those who are asking "What do I need to do to protect myself from this issue, right now?"
The options out there for managing it, are out there from Katech, and others.
Others who have a proven track record of managing it.
The most important thing is, that those options have proven to be effective, over time, and under extreme use.
This cannot be argued with.
People in the position of warranties running out, those ready to modify their cars, those planning on regularly tracking their cars such as Howie and others, those people have to take action, as opposed to anything else.
That is my point of view on this whole subject, and why, when I look at Jason's comment, I can understand fully what he meant by it.
Or more to the point, if one finds out they have according to the techniques described in this discussion, "bad geometry."
I am curious.
What do they then do? What is the plan? And who in here has implemented it? What kinds of results have they gotten, and under what circumstances?
People have been observing, and effectively dealing with the valve matter for years now.
Experts in their fields, many of them.
Perhaps I am looking at it with well, a jaundiced eye. But I tend to look at what we are seeing here, as well, reinventing the wheel.
I showed my own examples of my own heads. With shot exhaust guides in them.
Out of curiosity, what do you make of all of this?
I appreciate that. Because it's not.
I'm a little bit different in that regard.
I recall my first of several conversations with John Armstrong (Ranger), back when we started the initial C6 Z06 Fast List. He had taken a lot of heat from those who didn't particularly care for him or his methods.
Didn't like his driving tips, wanted him to release his data logs, etc.
One day, he told me, "Ricky, all I want is for people to get the most out of their cars."
That, has stuck with me.
As such, my greatest concern, is with those who do not have the luxury to merely discuss this matter, and discuss theories, but with those who actually have to do something about it, aside from "talking" about it.
Not those like yourself, whom I cannot for the life of me, see how they not only arrive at, but are convinced that there are supposedly "causes" aside from those already, if not outright known and discussed, then certainly show compelling evidence that they are at the root of this issue, and convinced even further, that GM and Katech are "hiding something" in an attempt to "thwart" those "investigating" it and trying to get at "the truth".
My goal is to help those who are asking "What do I need to do to protect myself from this issue, right now?"
The options out there for managing it, are out there from Katech, and others.
Others who have a proven track record of managing it.
The most important thing is, that those options have proven to be effective, over time, and under extreme use.
This cannot be argued with.
People in the position of warranties running out, those ready to modify their cars, those planning on regularly tracking their cars such as Howie and others, those people have to take action, as opposed to anything else.
That is my point of view on this whole subject, and why, when I look at Jason's comment, I can understand fully what he meant by it.
01-05-2013, 04:38 PM
#1823
But I think the "problem" if one can call it that, arose when I didn't respond to these questions with the answers you were perhaps looking for.
Last edited by '06 Quicksilver Z06; 01-05-2013 at 04:52 PM.
01-05-2013, 04:49 PM
#1824
Burning Brakes
This thread, and it's basic tenant, has been "revised" more times than I care to count.
I am well aware of said revisions as I was one of the ones who initially encouraged him to do so way back when.
http://forums.corvetteforum.com/c6-z...post1582426519
The revisions, of which there have been a few now, one I alluded to in my response to KLJ about recommended measurements which were discovered to be meaningless, are why I believe this whole matter, this entire thread, takes on a "half baked" appearance, and one which essentially involves a smorgasbord or "opinions", some of them outright "red herrings", such as the location of the valve cover hole, and simply thrown out there, to be "discussed", and to the benefit of really no one currently facing this matter, and having to do something about it at this time.
These ideas from seemingly out of left field, and seemingly in complete disregard to what we have witnessed over the last several years with regard to this matter in terms of outright failures, do a good job of lengthening the thread, but that is about it.
Indeed, the latest "opinion" we have now is in the rectangular nature of the underside of the rocker arm.
Again, very likely a red herring, resulting in people barking up the wrong tree, and adding another couple hundred posts to the thread, keeping it at the forefront, while some, due to the technojargon, see it as "scientific advancement", and accept it as such, all the while at the same time, people are out there and in positions where they have to actually act, to address this matter, as opposed to discuss theories about rectangles and such.
But I'll tell you what....discount everything I said above. Show me one person in here, who is tracking his car, out of warranty, who is willing to hang his hat, on ANY of what has been discussed in this thread to this point.
Go into the drag racing section, go into the road racing section. Find me anyone, aside from the OP, any C6 Z06 owner, who is willing to wager $17K on what has been "arrived at" and "gleaned" in here.
Find me the Z06 owner, who regularly tracks his car, or who has internal engine mods, who is willing to go out and use "the tool", pronounce that his "geometry" is OK, and then proceed to drive his car on the track, as hard as he always has.
What you will find, is most people from that group, are not going to trust the "scientific findings", and "talking" in this thread to "protect" them from catastrophe out there on the track, behind a broke $#*& dog.
I am well aware of said revisions as I was one of the ones who initially encouraged him to do so way back when.
http://forums.corvetteforum.com/c6-z...post1582426519
The revisions, of which there have been a few now, one I alluded to in my response to KLJ about recommended measurements which were discovered to be meaningless, are why I believe this whole matter, this entire thread, takes on a "half baked" appearance, and one which essentially involves a smorgasbord or "opinions", some of them outright "red herrings", such as the location of the valve cover hole, and simply thrown out there, to be "discussed", and to the benefit of really no one currently facing this matter, and having to do something about it at this time.
These ideas from seemingly out of left field, and seemingly in complete disregard to what we have witnessed over the last several years with regard to this matter in terms of outright failures, do a good job of lengthening the thread, but that is about it.
Indeed, the latest "opinion" we have now is in the rectangular nature of the underside of the rocker arm.
Again, very likely a red herring, resulting in people barking up the wrong tree, and adding another couple hundred posts to the thread, keeping it at the forefront, while some, due to the technojargon, see it as "scientific advancement", and accept it as such, all the while at the same time, people are out there and in positions where they have to actually act, to address this matter, as opposed to discuss theories about rectangles and such.
But I'll tell you what....discount everything I said above. Show me one person in here, who is tracking his car, out of warranty, who is willing to hang his hat, on ANY of what has been discussed in this thread to this point.
Go into the drag racing section, go into the road racing section. Find me anyone, aside from the OP, any C6 Z06 owner, who is willing to wager $17K on what has been "arrived at" and "gleaned" in here.
Find me the Z06 owner, who regularly tracks his car, or who has internal engine mods, who is willing to go out and use "the tool", pronounce that his "geometry" is OK, and then proceed to drive his car on the track, as hard as he always has.
What you will find, is most people from that group, are not going to trust the "scientific findings", and "talking" in this thread to "protect" them from catastrophe out there on the track, behind a broke $#*& dog.
You seem to be quite happy with your opinions and course of action you have embarked upon. Wonderful and I am happy for you.
Continuing to muck up what this thread is endeavoring to accomplish is counter productive..to those who are not convinced or in agreement with your opinions and your course of action(s)..in what you believe is a fix..
The revisions you reference is what is normally encountered in pursuit of knowledge..It represents a healthy and necessary ingredient when a problem is not readily evident..On the contrary, fanatically hanging on to a "solution" without factual evidence of the cause of failure is laughable...please no "IT'S THE GUIDES"...Perhaps you can respond with facts and proof to the last several threads asking pertinent questions...Why.
01-05-2013, 06:05 PM
#1825
I totally agree! I tried using the "ignore list" feature for the biggest derailer! but unfortunately if anyone answers him in quotes it still clogs up my page with his long winded rebuttals, pictures and quotes from years past. My suggestion is if you had said you opinion once...that should be sufficient enough for people to read and understand your views.
01-05-2013, 07:04 PM
#1826
Hi There,
I have spent several hours this afternoon looking at your pictures and data. Thank you for having the foresight to take them. One point I wanted to double check on -- did you re-install the heads in their original respective locations? I am not sure if they are location specific or can be swapped to either bank.
I assure you I did not just throw my comment out there.
We seem to operate on different time scales. There are questions that I have now spent decades thinking about.
I have spent several hours this afternoon looking at your pictures and data. Thank you for having the foresight to take them. One point I wanted to double check on -- did you re-install the heads in their original respective locations? I am not sure if they are location specific or can be swapped to either bank.
I assure you I did not just throw my comment out there.
We seem to operate on different time scales. There are questions that I have now spent decades thinking about.
Last edited by KLJ; 01-05-2013 at 07:09 PM.
01-05-2013, 07:12 PM
#1827
Hi There,
I have spent several hours this afternoon looking at your pictures and data. Thank you for having the foresight to take them. One point I wanted to double check on -- did you re-install the heads in their original respective locations? I am not sure if they are location specific or can be swapped to either bank.
I assure you I did not just throw my comment out there.
We seem to operate on different time scales. There are questions that I have now spent decades thinking about.
I have spent several hours this afternoon looking at your pictures and data. Thank you for having the foresight to take them. One point I wanted to double check on -- did you re-install the heads in their original respective locations? I am not sure if they are location specific or can be swapped to either bank.
I assure you I did not just throw my comment out there.
We seem to operate on different time scales. There are questions that I have now spent decades thinking about.
Of the heads if you are interested. But the whiners in here about dissenting opinions, I'm not interested in responding to them.
I'll send you a pm a little later.
Last edited by '06 Quicksilver Z06; 01-05-2013 at 07:14 PM.
01-05-2013, 07:22 PM
#1828
01-05-2013, 08:27 PM
#1829
Team Owner
Regarding GM's statement about a machining error in the valve guide and your related question "What other details would it be helpful to know?"-
That's easy. How about identifying whether it was guides bored to the wrong diameter, or installed off line laterally from the valve seat, or installed off angle in the other axis? This would make it much easier for us to determine if our particular motor has the problem, rather than relying on somebody like John to start from scratch and attempt to figure it out for all Z06 owners.
That's easy. How about identifying whether it was guides bored to the wrong diameter, or installed off line laterally from the valve seat, or installed off angle in the other axis? This would make it much easier for us to determine if our particular motor has the problem, rather than relying on somebody like John to start from scratch and attempt to figure it out for all Z06 owners.
01-05-2013, 09:56 PM
#1830
Melting Slicks
Also, note how one intake valve is gouged at the top. Apparently QA/QC missed that. So it doesn't suprise me that "GM's 100% inspection" of heads after Feb 2011 is just garbage talk.
01-05-2013, 10:36 PM
#1831
Le Mans Master
I totally agree! I tried using the "ignore list" feature for the biggest derailer! but unfortunately if anyone answers him in quotes it still clogs up my page with his long winded rebuttals, pictures and quotes from years past. My suggestion is if you had said you opinion once...that should be sufficient enough for people to read and understand your views.
01-05-2013, 10:48 PM
#1832
Burning Brakes
How about identifying whether it was guides bored to the wrong diameter, or installed off line laterally from the valve seat, or installed off angle in the other axis? This would make it much easier for us to determine if our particular motor has the problem, rather than relying on somebody like John to start from scratch and attempt to figure it out for all Z06 owners.
The answer is not a simple one, nor is the cause a single source. The "root" cause, however, is directly related to the guide. The geometry chase here, while a valid and interesting pursuit, is secondary and reveals another symptom and not the cause IMO.
Last edited by SS MPSTR; 01-05-2013 at 10:50 PM.
01-05-2013, 11:17 PM
#1833
Race Director
While we're waiting for John, or somebody else, to nail it down I'd love to hear what you think it is. I certainly don't know- I'm here in hopes of learning what it is. All we have so far is opinions and this kind of discussion might actually contribute something positive. I just don't see the downside, if you don't mind putting it out there.
01-06-2013, 04:22 AM
#1834
Thank you for the pics, Erick. My immediate suggestion is to take it to a top cylinder head specialist and carefully determine why so many of the springs are off-center with respect to the retainers. It seems like a sure recipe for guide wear.
I dont know if these help you. They are from my LSX-LS7 heads. I read somewhere that they were rotated, or vibrated during casting to prevent core shifting, but I can't find that article anymore.
Also, note how one intake valve is gouged at the top. Apparently QA/QC missed that. So it doesn't suprise me that "GM's 100% inspection" of heads after Feb 2011 is just garbage talk.
Also, note how one intake valve is gouged at the top. Apparently QA/QC missed that. So it doesn't suprise me that "GM's 100% inspection" of heads after Feb 2011 is just garbage talk.
01-06-2013, 10:01 AM
#1835
If the guide is initially reamed oversize (doesn't seem to be the issue, but for example) then the nature of the design would lead to rapid guide wear which would lead to -- bad geometry (the guide will wear in one direction due to side forces from the rocker action and eventually 'tilt' in that direction when acted upon by the rocker).
01-06-2013, 11:01 AM
#1836
Originally Posted by SS MPSTR
The answer is not a simple one, nor is the cause a single source. The "root" cause, however, is directly related to the guide. The geometry chase here, while a valid and interesting pursuit, is secondary and reveals another symptom and not the cause IMO.
If the guide is initially reamed oversize (doesn't seem to be the issue, but for example) then the nature of the design would lead to rapid guide wear which would lead to -- bad geometry (the guide will wear in one direction due to side forces from the rocker action and eventually 'tilt' in that direction when acted upon by the rocker).
Having a crown would allow for more leeway for slight relative location errors of the longitudinal axes of the pedestal bolt and valve stem* as a point contact would be present rather than a line contact at the stem face. But along with this "forgiveness" would come a cost: the point contact would be imparting a lateral unwanted torque component that would cause wear in the guide. The further the point travels from the center of the valve stem tip the greater the lateral torque "bending" components.
* errors side to side or fore and aft or a combination.
Last edited by KLJ; 01-06-2013 at 11:07 AM. Reason: grammar
01-06-2013, 02:06 PM
#1837
In again researching the topic, I found some more information that I am sure has been thrashed in other threads and to some extent in this thread. It bears revisiting, however, and with your engine in particular.
http://www.epi-eng.com/aircraft_engi...te_engines.htm has a review from 6-7 years ago on the suitability of the LS-7 as an aircraft powerplant.
Strikingly prescient; my emphasis:
The reason we think the stock engine should be limited to avgas is that the high 11:1 static compression ratio and sustained full-throttle operation near peak torque will produce very high cylinder pressures which will invite detonation on mogas. The ECU strategy for dealing with detonation is based on the occurrence of transient events, and is handled by removing spark advance until the incipient detonation subsides. That is fine for an automotive transient, but causes EGT to rise dramatically, which is not terribly good for exhaust valve life.
In light of this, the proper question appears to be: did GM perform long term durability studies with the engine operating on low octane or marginally acceptable fuel? Why would they?
Possibly you and the previous owner of the engine donor Corvette and the rest of the owners reading this are the dataset for operating in this manner. Gasoline supplies are extremely variable.
Slight bolt-on mods like headers, cold air intake and a tune should be expected to have long term deleterious effects if the engine/fuel management system is already tweaked and the manner in which it protects itself has the side effect of raising exhaust temperatures. That information is not going to be too popular, unfortunately.
Last edited by KLJ; 01-06-2013 at 02:11 PM. Reason: spelling
01-06-2013, 02:39 PM
#1839
Burning Brakes
I can't see why the two would be mutually exclusive... if the guide is installed or reamed crooked, then that would case a geometry problem.
If the guide is initially reamed oversize (doesn't seem to be the issue, but for example) then the nature of the design would lead to rapid guide wear which would lead to -- bad geometry (the guide will wear in one direction due to side forces from the rocker action and eventually 'tilt' in that direction when acted upon by the rocker).
If the guide is initially reamed oversize (doesn't seem to be the issue, but for example) then the nature of the design would lead to rapid guide wear which would lead to -- bad geometry (the guide will wear in one direction due to side forces from the rocker action and eventually 'tilt' in that direction when acted upon by the rocker).
Don't take this the wrong way, but I really don't care if anyone agrees or disagrees with my opinion on this - and it's just that, an opinion. In doing my own research and after talking to many well respected cylinder head guys - both familiar with the LS7 valve issue and not so familiar with the specifics of the LS7 head - I have come to the conclusion on what's best for me to do to alleviate the concern of losing a $15k engine, due to guides that are too short. The above (albeit condensed) explanation is logical to me and the solution is new guides with SS exhaust valves. How many new guide/exhaust valve failures have been reported? How many bronze guides measured out of spec after this re-work?
I think Jason at Katech was right on the money with his responses about this issue, but the things people are chasing (and arguing about in over 1500 posts within various threads) are symptoms, not the cause. Replacing the guides is the solution, not a band-aid.
FWIW, the Brodix heads are identical in geometry and size of installed components as the factory LS7 units. I'm not saying they are a bad head choice (an excellent one, actually), but to avoid a false sense of security, I would check the lengths of the components. Unless you're doing some big build, the stock heads will support a ton of power, reliably.
Whether GM should do anything about this issue now for the 25k+ cars out there is another debate altogether.
Happy Motoring.
01-06-2013, 02:42 PM
#1840
Burning Brakes
I did look at all the data and pictures for an extended period of time -- I would have to say honestly that possible core shift could be an aggravating factor in all this but not the primary or root cause.
In again researching the topic, I found some more information that I am sure has been thrashed in other threads and to some extent in this thread. It bears revisiting, however, and with your engine in particular.
http://www.epi-eng.com/aircraft_engi...te_engines.htm has a review from 6-7 years ago on the suitability of the LS-7 as an aircraft powerplant.
Strikingly prescient; my emphasis:
Indeed, over seven years ago on this very website another prescient discussion took place on the fuel requirements for the LS-7: http://forums.corvetteforum.com/c6-z...uirements.html
In light of this, the proper question appears to be: did GM perform long term durability studies with the engine operating on low octane or marginally acceptable fuel? Why would they?
Possibly you and the previous owner of the engine donor Corvette and the rest of the owners reading this are the dataset for operating in this manner. Gasoline supplies are extremely variable.
Slight bolt-on mods like headers, cold air intake and a tune should be expected to have long term deleterious effects if the engine/fuel management system is already tweaked and the manner in which it protects itself has the side effect of raising exhaust temperatures. That information is not going to be too popular, unfortunately.
In again researching the topic, I found some more information that I am sure has been thrashed in other threads and to some extent in this thread. It bears revisiting, however, and with your engine in particular.
http://www.epi-eng.com/aircraft_engi...te_engines.htm has a review from 6-7 years ago on the suitability of the LS-7 as an aircraft powerplant.
Strikingly prescient; my emphasis:
Indeed, over seven years ago on this very website another prescient discussion took place on the fuel requirements for the LS-7: http://forums.corvetteforum.com/c6-z...uirements.html
In light of this, the proper question appears to be: did GM perform long term durability studies with the engine operating on low octane or marginally acceptable fuel? Why would they?
Possibly you and the previous owner of the engine donor Corvette and the rest of the owners reading this are the dataset for operating in this manner. Gasoline supplies are extremely variable.
Slight bolt-on mods like headers, cold air intake and a tune should be expected to have long term deleterious effects if the engine/fuel management system is already tweaked and the manner in which it protects itself has the side effect of raising exhaust temperatures. That information is not going to be too popular, unfortunately.
It also reminds me that many have also pointed out over the year the very rich AFR in the stock tune.
Last edited by Rock36; 01-06-2013 at 04:30 PM.