[Z06] Valve Issues?
05-02-2013, 12:35 PM
#21
Melting Slicks
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Thanks for the reply Jason.
About the concentricity problem, how can we check for this (with the head off and disassembled of course) and how can it be corrected?
And can you other guys stop arguing for just a minute please? We might learn something here.
About the concentricity problem, how can we check for this (with the head off and disassembled of course) and how can it be corrected?
And can you other guys stop arguing for just a minute please? We might learn something here.
Last edited by wjnjr; 05-02-2013 at 12:37 PM.
05-02-2013, 12:36 PM
#22
Drifting
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GM has stated that there was a machining error on 2009-2011 LS7s (LS9's too but I'm not sure if GM specified that) that caused the valve guide to be machined non-concentric to the valve seat. We have found that this rapidly accelerates valve guide wear. The valve rocks in the guide and wears it out in an hourglass shape. The more it rocks, the more it wears in that manner. So far we've caught some very bad wear before the valve breaks, but if left untreated, the rocking in the guide is so severe that it fatigues the head of the valve until it fails. Every time the valve opens and closes its getting bent slightly in a different direction, working the stem around the base of the valve head.
Now, if I was involved in a cover-up with GM I wouldn't tell you the following. We recently saw high valve guide wear in 2007s and 2008s, so I'm not so sure that this is captured only in 2009-2011s.
A recent build, which I will post about soon, had massive (and I mean massive) intake guide wear. We caught it just in time. Now why would this be happening if it's just a defective exhaust valve? It's because it's not. It's a guide machining problem which could be on the intake OR exhaust OR both.
Now, if I was involved in a cover-up with GM I wouldn't tell you the following. We recently saw high valve guide wear in 2007s and 2008s, so I'm not so sure that this is captured only in 2009-2011s.
A recent build, which I will post about soon, had massive (and I mean massive) intake guide wear. We caught it just in time. Now why would this be happening if it's just a defective exhaust valve? It's because it's not. It's a guide machining problem which could be on the intake OR exhaust OR both.
I have 7 sets of heads with the guides toasted on the exhaust side. in fact I've yet to see an intake guide past .0056" of wear and i got that a few days ago. but I've seen .0160 on the exhaust. also what about the 06 cars ?
Last edited by z0sicktanner; 05-03-2013 at 12:35 AM.
05-02-2013, 12:36 PM
#23
crickets.....body slam....
05-02-2013, 12:38 PM
#24
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For all myself or anyone else knows, as a result of that relationship, you could be privy to information which the other vendors are not.
Why did you immediately assume, that because I pointed out that relationship, that I was necessarily implying that you were using an "inferior valve" when I said nothing of the sort in my response to him?
Why did you immediately assume, that because I pointed out that relationship, that I was necessarily implying that you were using an "inferior valve" when I said nothing of the sort in my response to him?
05-02-2013, 12:40 PM
#25
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I didn't "imply" anything of the sort, but only stated a point of fact, and that is that your company does maintain a working relationship with General Motors. In other words, GM is one if your clients.
Or is that not true?
Because if it is, then every man in here can infer what, if anything that would mean to him.
Or is that not true?
Because if it is, then every man in here can infer what, if anything that would mean to him.
You may not have intended to imply it but the way you worded your previous response certainly implied that Katech did choose inferior parts based on a business relationship.
You and many others have known from previous posts over the last two years or so that Katech has stated time and time again that they believe it is a guide issue and not a valve issue and could have added that to your post. The fact they state it is a guide issue shows they aren't sugar coating an issue because GM is a large Customer.
Bill
05-02-2013, 12:42 PM
#26
Drifting
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if it was a concentricity problem the head guys would have caught it. and there has already been heads fail that have been reworked to fix this so called concentricity problem
05-02-2013, 12:42 PM
#27
Safety Car
Now, if I was involved in a cover-up with GM I wouldn't tell you the following. We recently saw high valve guide wear in 2007s and 2008s, so I'm not so sure that this is captured only in 2009-2011s.
A recent build, which I will post about soon, had massive (and I mean massive) intake guide wear.
A recent build, which I will post about soon, had massive (and I mean massive) intake guide wear.
We are all seeing guide wear in 2006 - 2008 models, 2009-2011 admitted by GM and 2012+ too.
The defective part of the exhaust valve is that it breaks much sooner. It doesn't take a lot of rockin to get it knockin( its way out of the block).
The real difference: intake guide wear does not quickly lead to worn or broken intake valve. Exhaust guide wear does.
All my guides were worn. Only my exhaust valves were worn. Thus the EXTRA rockin in the exhaust valve.
So maybe we can call the exhaust valve weak or under designed for the application.
We have titanium valves, stainless hollow oem, stainless solid aftermarket , powdered medal guides and bronze guides. All dissimilar metals reacting to each other differently.
We are seeing oem exhaust valves wearing with the guides, Titanium valves wearing into the guides, and bronze/SS with minimal wear.
This suggests it IS a guide problem as GM admitted.
HOWEVER the cause of the hole in your block is the weak valve broken BY the GUIDE problem.
Last edited by jedblanks; 05-02-2013 at 12:53 PM.
05-02-2013, 12:44 PM
#28
Premium Supporting Vendor
hmm I remember 2 years ago you said just because it has guide wear doesn't mean it will fail..the tune has changed I see. I've seen some intake guide wear but not much. I have 7 sets of heads with the guides toasted on the exhaust side only. in fact I've yet to see an intake guide past .0056" of wear. but I've seen .0160 on the exhaust. also what about the 06 cars ?
Science is a beautiful thing. It allows you to change your opinion when new empirical evidence presents itself that changes your outlook on a topic.
05-02-2013, 12:51 PM
#29
Premium Supporting Vendor
We are all seeing guide wear in 2006 - 2008 models, 2009-2011 admitted by GM and 2012+ too.
The defective part of the exhaust valve is that it breaks much sooner. It doesn't take a lot of rockin to get it knockin( its way out of the block).
The real difference: intake guide wear does not quickly lead to worn or broken intake valve. Exhaust guide wear does.
All my guides were worn. Only my exhaust valves were worn. Thus the EXTRA rockin in the exhaust valve.
So maybe we can call the exhaust valve weak or under designed for the application.
The defective part of the exhaust valve is that it breaks much sooner. It doesn't take a lot of rockin to get it knockin( its way out of the block).
The real difference: intake guide wear does not quickly lead to worn or broken intake valve. Exhaust guide wear does.
All my guides were worn. Only my exhaust valves were worn. Thus the EXTRA rockin in the exhaust valve.
So maybe we can call the exhaust valve weak or under designed for the application.
05-02-2013, 12:52 PM
#30
Drifting
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why don't we see this in ls1 ls2 ls6 lq9 ls3? because one thing is for sure it's not happening. all my guides are in spec after 22k miles beat the hell out of miles at that. not one has wear with the bronze an ss intake or exhaust with a 675 lift cam. also I'm glad you guys figured it out right after they stoped making the c6z
Last edited by z0sicktanner; 05-02-2013 at 09:42 PM.
05-02-2013, 12:54 PM
#31
Premium Supporting Vendor
The concentricity problem will present itself as guide wear rather quickly. I've seen it as low as 3000 miles. It can be fixed by replacing the guide and re-machining.
05-02-2013, 12:55 PM
#32
Safety Car
We are all seeing guide wear in 2006 - 2008 models, 2009-2011 admitted by GM and 2012+ too.
The defective part of the exhaust valve is that it breaks much sooner. It doesn't take a lot of rockin to get it knockin( its way out of the block).
The real difference: intake guide wear does not quickly lead to worn or broken intake valve. Exhaust guide wear does.
All my guides were worn. Only my exhaust valves were worn. Thus the EXTRA rockin in the exhaust valve.
So maybe we can call the exhaust valve weak or under designed for the application.
The defective part of the exhaust valve is that it breaks much sooner. It doesn't take a lot of rockin to get it knockin( its way out of the block).
The real difference: intake guide wear does not quickly lead to worn or broken intake valve. Exhaust guide wear does.
All my guides were worn. Only my exhaust valves were worn. Thus the EXTRA rockin in the exhaust valve.
So maybe we can call the exhaust valve weak or under designed for the application.
05-02-2013, 12:56 PM
#33
Safety Car
05-02-2013, 12:59 PM
#34
Melting Slicks
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So will a "normal" valve job procedure on the seats correct it or does it require something more extensive?
05-02-2013, 01:06 PM
#35
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05-02-2013, 01:09 PM
#37
05-02-2013, 01:26 PM
#38
Drifting
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does it matter? they failed from dropped exhaust valves...I'm still waiting on what my so called conspiracy theory is? I said I was seeing a ton of guide wear and motors dropping valves. well your guides are bad to....how in the hell was that a conspiracy theory? I knew the day would come that ppl would understand why I posted what I did..and I'm just one guy that ports a small number of ls7 heads and I knew without doubt there was an still is a huge proplem. mybe it's time to throw pies in faces because I feel good about what I found and the posts I made. I saved more than a few engines.
Last edited by z0sicktanner; 05-02-2013 at 01:30 PM.
05-02-2013, 01:33 PM
#39
Ligenfelter did GM warranty work on an LT5 that I once owned, so maybe I don't need to look. But that proves no half-baked conspiracy theory. Your and Quick's attempts to discredit certain vendors (and others) who do not subscribe to your 'crap' OEM exhaust valve theory are quite transparent and lacking, both in substance and logic.
yeah on his dime and not GM... thats just wrong