Z06 drops valve
11-01-2017, 01:53 PM
#41
Team Owner
By failure I mean an engine that has to be repaired. Not voluntarily, proactively repaired, but it stopped working or started making a bad noise or whatever. I'm sure many engine parts wear over the life of the engine. And some will matter much more than others.
Don't get me wrong, I'm all about preventive maintenance. But if we are talking about a 1% chance, it makes no sense (to me) to spend $2,000. How many do you think have failed?
Actually, if a new engine costs $15,000, the only way the math makes sense is if I have a greater than 13% chance of failure. I just can't believe it is anywhere near that. Not to mention that if I replace it, I get a new engine. Fixing the heads does not give me a new engine.
Don't get me wrong, I'm all about preventive maintenance. But if we are talking about a 1% chance, it makes no sense (to me) to spend $2,000. How many do you think have failed?
Actually, if a new engine costs $15,000, the only way the math makes sense is if I have a greater than 13% chance of failure. I just can't believe it is anywhere near that. Not to mention that if I replace it, I get a new engine. Fixing the heads does not give me a new engine.
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Seven11 (11-05-2017)
11-01-2017, 01:54 PM
#42
Le Mans Master
Thread Starter
What doesn't make sense to me is that you are willing to spend big $$$ to buy a Z06, then unwilling to spend $2000 to make sure something doesn't happen to it. Had you rather spend $15000 + or $2000??? What if you are in that less than 1%??? Or you just hope it happens to someone else, not you?
11-01-2017, 02:00 PM
#43
Team Owner
11-01-2017, 02:04 PM
#44
Well the numbers can't give you a correct algorithm because almost every car had valve guide issues with the guides wearing. Now dropping valves that's another percent.....I would base on how many cars were made how many dropped a valve which we don't know and how many need preparing before the issue....
11-01-2017, 03:00 PM
#45
Le Mans Master
Thread Starter
The other side of the coin is that everyone who owns a 427 (coupe, convertible) is not on this forum. We don't know how many have had engine failure, nor will we ever know. From 2006-2013, approximately 30, 484 Corvettes with 427's in them (Z06 and convertibles) have been built. How many are still on the road, have not been flooded, wrecked (totalled), engines removed for various reasons, modded to be drag raced or road raced, or any other thing you can think of are simply not known. What we know is that they do have problems with the valves. Fixing that problem just makes good sense.
11-01-2017, 03:28 PM
#46
Racer
So if we know of 100 failures out of 28,000 produced, that is about 0.3% failure rate? And every car has this issue? Please discuss if my numbers are wrong or whatever. I'm just curious. Even if it is 300 failures, that is still only 1%, correct?
I'm just thinking that if I have a 99% chance of making it to 50,000 miles or even 100,000 miles, I'm not spending $2,000 on the heads.
I'm just thinking that if I have a 99% chance of making it to 50,000 miles or even 100,000 miles, I'm not spending $2,000 on the heads.
By failure I mean an engine that has to be repaired. Not voluntarily, proactively repaired, but it stopped working or started making a bad noise or whatever. I'm sure many engine parts wear over the life of the engine. And some will matter much more than others.
Don't get me wrong, I'm all about preventive maintenance. But if we are talking about a 1% chance, it makes no sense (to me) to spend $2,000. How many do you think have failed?
Actually, if a new engine costs $15,000, the only way the math makes sense is if I have a greater than 13% chance of failure. I just can't believe it is anywhere near that. Not to mention that if I replace it, I get a new engine. Fixing the heads does not give me a new engine.
I work on rocket engines for a living, and a big part of that is managing risk. Sometimes risk is acceptable. It just has to be evaluated. I'm trying to evaluate it.
Don't get me wrong, I'm all about preventive maintenance. But if we are talking about a 1% chance, it makes no sense (to me) to spend $2,000. How many do you think have failed?
Actually, if a new engine costs $15,000, the only way the math makes sense is if I have a greater than 13% chance of failure. I just can't believe it is anywhere near that. Not to mention that if I replace it, I get a new engine. Fixing the heads does not give me a new engine.
I work on rocket engines for a living, and a big part of that is managing risk. Sometimes risk is acceptable. It just has to be evaluated. I'm trying to evaluate it.
But for the sake of discussion, let's say only 100 Z's have had catastrophic failure due to the valve guide issue (the 427 verts, Camaro LS7's and even LS9's are starting to pop up now too though). Yes, that is a low absolute number of failures. However, how many have simply not shown up yet due to low mileage/use and a lack of owner knowledge to, or lack of willingness to, get the heads inspected? Until boom. Now, how many others have not shown up due to owners' being proactive and getting the heads inspected and subsequently reworked? Again, we simply won't ever know.
The true failure issue, however, is the guides being outside GM's service limit prematurely. Not just catastrophic failure, which is caused by the true failure found in the guide wear. The service limit is supposed to last at least 100k miles given normal DD type use. How far out of this limit can you go before it goes boom? No one knows. Care to gamble $15000+ to find out? These cars for the most part are driven very little. This means that issues would likely not start popping up for a long time, which would result in a seemingly low failure rate. But, after several reported failures and reports of inspected heads being out of spec, thousands of owners over the years have been subsequently inspecting or reworking/replacing their OE heads. These valve guides are being inspected and found to be out of spec even when brand new from GM. This type of failure makes up far more than 1%. And again, this brings us back to the question of how many catastrophic failures have been prevented due to owner diligence in getting the heads inspected/reworked/replaced.
So many cases of this type of failure have been documented that Katech even goes as far as to say (it was in a magazine article written by Jason a few months back) that ALL LS7 engines should at least be inspected. No one is saying that you absolutely must rework the heads or replace them in every single car out there. They should however be inspected at the very least. You can outright gamble with it and never inspect them, or spend a couple hundred bucks to inspect them and find out for sure. If they check safely within the service limit, then slap it back together and carry on (I personally would inspect them again at some future interval to be sure there is no accelerated wear). If they are outside the limit or very close to it early in the vehicles' life (mileage wise that is), fix them. If they were within spec under/near 100k miles, but are outside the limit after 100k miles on a normally driven vehicle (no hard track time), then I would consider that normal service life.
The engines themselves are not the issue, accelerated guide wear is. So no, fixed heads do not give you a new engine, but that new engine is very likely to still have bad heads.
Hopefully that made sense and helps with your evaluation. I'm a little tired so it may seem a bit like rambling. If it does, I apologize.
11-01-2017, 03:55 PM
#47
Race Director
We don't know how many catastrophic failures there have been total, but there have been so many just on this one forum. Not to mention that numerous members here know several (3+) people, not on this forum that are not just on engine #2, but actually on engine #3. And all of that doesn't take into account those people that we don't know about. Plus, there are hundreds if not more that have been removed entirely due to mods/flood/wrecks/etc. that the percentages just fall apart.
But for the sake of discussion, let's say only 100 Z's have had catastrophic failure due to the valve guide issue (the 427 verts, Camaro LS7's and even LS9's are starting to pop up now too though). Yes, that is a low absolute number of failures. However, how many have simply not shown up yet due to low mileage/use and a lack of owner knowledge to, or lack of willingness to, get the heads inspected? Until boom. Now, how many others have not shown up due to owners' being proactive and getting the heads inspected and subsequently reworked? Again, we simply won't ever know.
The true failure issue, however, is the guides being outside GM's service limit prematurely. Not just catastrophic failure, which is caused by the true failure found in the guide wear. The service limit is supposed to last at least 100k miles given normal DD type use. How far out of this limit can you go before it goes boom? No one knows. Care to gamble $15000+ to find out? These cars for the most part are driven very little. This means that issues would likely not start popping up for a long time, which would result in a seemingly low failure rate. But, after several reported failures and reports of inspected heads being out of spec, thousands of owners over the years have been subsequently inspecting or reworking/replacing their OE heads. These valve guides are being inspected and found to be out of spec even when brand new from GM. This type of failure makes up far more than 1%. And again, this brings us back to the question of how many catastrophic failures have been prevented due to owner diligence in getting the heads inspected/reworked/replaced.
So many cases of this type of failure have been documented that Katech even goes as far as to say (it was in a magazine article written by Jason a few months back) that ALL LS7 engines should at least be inspected. No one is saying that you absolutely must rework the heads or replace them in every single car out there. They should however be inspected at the very least. You can outright gamble with it and never inspect them, or spend a couple hundred bucks to inspect them and find out for sure. If they check safely within the service limit, then slap it back together and carry on (I personally would inspect them again at some future interval to be sure there is no accelerated wear). If they are outside the limit or very close to it early in the vehicles' life (mileage wise that is), fix them. If they were within spec under/near 100k miles, but are outside the limit after 100k miles on a normally driven vehicle (no hard track time), then I would consider that normal service life.
The engines themselves are not the issue, accelerated guide wear is. So no, fixed heads do not give you a new engine, but that new engine is very likely to still have bad heads.
Hopefully that made sense and helps with your evaluation. I'm a little tired so it may seem a bit like rambling. If it does, I apologize.
But for the sake of discussion, let's say only 100 Z's have had catastrophic failure due to the valve guide issue (the 427 verts, Camaro LS7's and even LS9's are starting to pop up now too though). Yes, that is a low absolute number of failures. However, how many have simply not shown up yet due to low mileage/use and a lack of owner knowledge to, or lack of willingness to, get the heads inspected? Until boom. Now, how many others have not shown up due to owners' being proactive and getting the heads inspected and subsequently reworked? Again, we simply won't ever know.
The true failure issue, however, is the guides being outside GM's service limit prematurely. Not just catastrophic failure, which is caused by the true failure found in the guide wear. The service limit is supposed to last at least 100k miles given normal DD type use. How far out of this limit can you go before it goes boom? No one knows. Care to gamble $15000+ to find out? These cars for the most part are driven very little. This means that issues would likely not start popping up for a long time, which would result in a seemingly low failure rate. But, after several reported failures and reports of inspected heads being out of spec, thousands of owners over the years have been subsequently inspecting or reworking/replacing their OE heads. These valve guides are being inspected and found to be out of spec even when brand new from GM. This type of failure makes up far more than 1%. And again, this brings us back to the question of how many catastrophic failures have been prevented due to owner diligence in getting the heads inspected/reworked/replaced.
So many cases of this type of failure have been documented that Katech even goes as far as to say (it was in a magazine article written by Jason a few months back) that ALL LS7 engines should at least be inspected. No one is saying that you absolutely must rework the heads or replace them in every single car out there. They should however be inspected at the very least. You can outright gamble with it and never inspect them, or spend a couple hundred bucks to inspect them and find out for sure. If they check safely within the service limit, then slap it back together and carry on (I personally would inspect them again at some future interval to be sure there is no accelerated wear). If they are outside the limit or very close to it early in the vehicles' life (mileage wise that is), fix them. If they were within spec under/near 100k miles, but are outside the limit after 100k miles on a normally driven vehicle (no hard track time), then I would consider that normal service life.
The engines themselves are not the issue, accelerated guide wear is. So no, fixed heads do not give you a new engine, but that new engine is very likely to still have bad heads.
Hopefully that made sense and helps with your evaluation. I'm a little tired so it may seem a bit like rambling. If it does, I apologize.
I'm just wondering if people panic because there is a (low) risk. There is always a risk of engine failure, no matter what you drive.
11-01-2017, 04:00 PM
#49
Race Director
My point is, we always have risk. And the cost (impact) of a failure goes into the analysis. Along with the frequency of occurrence. A rare event with catastrophic consequences is often accepted, if it is believed to be rare enough.
Some of us want to "fix" everything we know of and remove all known risk. In reality, you can never remove all risk. If the cost of the fix is high and the frequency of occurrence is low (such as in this discussion), the best course may be to just accept the risk.
Now, in this case we might be able to reduce the risk even further by inspection. That sounds like a reasonable course of action.
Last edited by Tonylmiller; 11-01-2017 at 04:01 PM.
11-01-2017, 04:04 PM
#50
Race Director
What doesn't make sense to me is that you are willing to spend big $$$ to buy a Z06, then unwilling to spend $2000 to make sure something doesn't happen to it. Had you rather spend $15000 + or $2000??? What if you are in that less than 1%??? Or you just hope it happens to someone else, not you?
Would I rather have a 0.5% chance of paying $15,000, or a 100% chance of paying $2,000? The better course of action would normally to be to accept the risk.
0.005 x $15,000 is only $75. That is a LOT less than $2,000.
By the way, it is a Convertible "Z06".
Last edited by Tonylmiller; 11-01-2017 at 04:07 PM.
11-01-2017, 05:34 PM
#51
Team Owner
I'm a Systems Engineer, so I get involved in a lot of things. Especially when things go wrong.
My point is, we always have risk. And the cost (impact) of a failure goes into the analysis. Along with the frequency of occurrence. A rare event with catastrophic consequences is often accepted, if it is believed to be rare enough.
Some of us want to "fix" everything we know of and remove all known risk. In reality, you can never remove all risk. If the cost of the fix is high and the frequency of occurrence is low (such as in this discussion), the best course may be to just accept the risk.
Now, in this case we might be able to reduce the risk even further by inspection. That sounds like a reasonable course of action.
My point is, we always have risk. And the cost (impact) of a failure goes into the analysis. Along with the frequency of occurrence. A rare event with catastrophic consequences is often accepted, if it is believed to be rare enough.
Some of us want to "fix" everything we know of and remove all known risk. In reality, you can never remove all risk. If the cost of the fix is high and the frequency of occurrence is low (such as in this discussion), the best course may be to just accept the risk.
Now, in this case we might be able to reduce the risk even further by inspection. That sounds like a reasonable course of action.
Still amazes me that there are people out there who know of the issue, but wont even have a simple look under the valve cover to assess the situation.
Here's a DIY thread on a wiggle test...unfortunately its been impaired by the Photobucket extortion tactics. https://www.corvetteforum.com/forums...-test-diy.html
Last edited by MTPZ06; 11-01-2017 at 05:38 PM.
11-01-2017, 09:49 PM
#52
Race Director
This past weekend at a road course and once on the highway the week before I got mis-fire under heavy throttle at around 4K RPm (no codes, but much of that was turned off when the HCI tune was done). I have been trouble shooting that this week. So far, spark plugs look super, resistance on all coil/spark plug wires is good. I pulled the valve covers and did a quick look there and things looked good. Tonight while doing some finishing up work, I checked the bolts on the MSD intake and many seemed loose, so I tightened virtually all of them. I will check out the car tomorrow and see if the problem has been solved or if it needs further diagnosis by someone more skilled than myself.
UPDATE: tightening the bolts on the MSD intake seems to have cured the mis-fire problem. I will do another road course event 11/24 and confirm all is well.
Presuming this issue gets resolved, I would plan to at least have the wiggle test done at 20K miles. I haven't decided if I'd have the PSI 1511 springs checked or not.
Long answer but the details are worth passing on.
Last edited by AzDave47; 11-15-2017 at 10:17 AM. Reason: changed to 9K miles
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MTPZ06 (11-01-2017)
11-01-2017, 10:15 PM
#53
Team Owner
I'm coming up on 10K miles on the build. I had CPR do a quick look a month ago when they installed my ARH 2" headers and ID725 injectors.
This past weekend at a road course and once on the highway the week before I got mis-fire under heavy throttle at around 4K RPm (no codes, but much of that was turned off when the HCI tune was done). I have been trouble shooting that this week. So far, spark plugs look super, resistance on all coil/spark plug wires is good. I pulled the valve covers and did a quick look there and things looked good. Tonight while doing some finishing up work, I checked the bolts on the MSD intake and many seemed loose, so I tightened virtually all of them. I will check out the car tomorrow and see if the problem has been solved or if it needs further diagnosis by someone more skilled than myself.
Presuming this issue gets resolved, I would plan to at least have the wiggle test done at 20K miles. I haven't decided if I'd have the PSI 1511 springs checked or not.
Long answer but the details are worth passing on.
This past weekend at a road course and once on the highway the week before I got mis-fire under heavy throttle at around 4K RPm (no codes, but much of that was turned off when the HCI tune was done). I have been trouble shooting that this week. So far, spark plugs look super, resistance on all coil/spark plug wires is good. I pulled the valve covers and did a quick look there and things looked good. Tonight while doing some finishing up work, I checked the bolts on the MSD intake and many seemed loose, so I tightened virtually all of them. I will check out the car tomorrow and see if the problem has been solved or if it needs further diagnosis by someone more skilled than myself.
Presuming this issue gets resolved, I would plan to at least have the wiggle test done at 20K miles. I haven't decided if I'd have the PSI 1511 springs checked or not.
Long answer but the details are worth passing on.
11-02-2017, 09:36 AM
#54
Team Owner
Any of the two piece plastic intakes need care and to be checked regularly.
11-02-2017, 10:40 AM
#55
Melting Slicks
I attended a FunFest Seminar in Effingham this past September. Subject was Z06/ZR1 maintenance put on by GM Tech Paul Koerner. This guy is totally in the tank for GM, denies there's a problem with Z06 heads by stating that warranty claims are less than 1%. Well, as we all know most of these failures occur out of warranty. He knows that - it's just his way of protecting GM. Same guy says that one piece brake pads are a mistake. I've got Carbotech one piece pads instead of the padlets and they perform fine with much less dust. By chance anyone else at that seminar?
$.02 deposited
$.02 deposited
Last edited by Tigershark3; 11-02-2017 at 11:24 AM.
11-02-2017, 09:58 PM
#57
Le Mans Master
Thread Starter
It is not that simple. It is in the math.
Would I rather have a 0.5% chance of paying $15,000, or a 100% chance of paying $2,000? The better course of action would normally to be to accept the risk.
0.005 x $15,000 is only $75. That is a LOT less than $2,000.
By the way, it is a Convertible "Z06".
Would I rather have a 0.5% chance of paying $15,000, or a 100% chance of paying $2,000? The better course of action would normally to be to accept the risk.
0.005 x $15,000 is only $75. That is a LOT less than $2,000.
By the way, it is a Convertible "Z06".
It "IS" that simple. You are an engineer. Everything has to make sense by the numbers for you. Did you do the math when you proposed to your wife or when you had kids? Divorce rate these days is mid 40%. Kids doing drugs probably higher than that.
And so its a "convertible" Z06. (I don't know where that came from). It still has the same 427 engine in that comes in coupe Z06's.
In my world where I don't make 6 figures, I had rather spend $2000 than take a chance on spending $15000+. I guess we think different.
11-02-2017, 10:08 PM
#58
Race Director
Re my posts above, tightening the bolts on the MSD intake did resolve the mis-fire issue.
11-02-2017, 11:06 PM
#59
Race Director
It "IS" that simple. You are an engineer. Everything has to make sense by the numbers for you. Did you do the math when you proposed to your wife or when you had kids? Divorce rate these days is mid 40%. Kids doing drugs probably higher than that.
And so its a "convertible" Z06. (I don't know where that came from). It still has the same 427 engine in that comes in coupe Z06's.
In my world where I don't make 6 figures, I had rather spend $2000 than take a chance on spending $15000+. I guess we think different.
And so its a "convertible" Z06. (I don't know where that came from). It still has the same 427 engine in that comes in coupe Z06's.
In my world where I don't make 6 figures, I had rather spend $2000 than take a chance on spending $15000+. I guess we think different.
11-03-2017, 12:02 AM
#60
Burning Brakes
All this math is ridiculous considering you don't have reliable data to use. If you did enough research and checked the wear on some cars yourself you wouldn't haven't created a thread to justify not doing head work. The mileage on most these cars is low so just cause they haven't blown up yet shouldn't make you feel good. Why don't you look at how many people have checked their guides and found them to be in spec cause that number is very low.
Also, you can check your guides for free so stop throwing around the $2000 number. If your guides are miraculously in spec then don't touch them and I would agree the risk is low and you'll be out no money. I'd continue to check them as you rack up miles though.
I checked mine when stock at 14k miles and they were pretty darn bad. I wanted more power anyways so it was a no brainier.
Also, you can check your guides for free so stop throwing around the $2000 number. If your guides are miraculously in spec then don't touch them and I would agree the risk is low and you'll be out no money. I'd continue to check them as you rack up miles though.
I checked mine when stock at 14k miles and they were pretty darn bad. I wanted more power anyways so it was a no brainier.
Last edited by rio95; 11-03-2017 at 12:05 AM.