Originally Posted by erick_e

My engine was built on 12 May 2009, and VIN build date was 28 May 2009.

Originally Posted by NWbluez06

I do not post much, but I do like to surf the forum alot. I hate the sky is falling threads, all the BS posts you have to dig though to get to the "meat" of the disscussion. That said... I do learn from the discourse here. So here is my contribution on this subject... I have a Oct. 2005 build date. I first tuned my Z06 in the spring of 06, drove it with 476rwhp till spring of 08 and with appox. 22,000 miles on it and no issues, I cammed it milled the heads for a 1/2 point increase in compression, and put SS exaust valves in, as well as springs ect... I also put a larger radator in ( temps on track were getting a little to hot at times with 250+ degree oil), lingenfelter tank, as well as other track mods. Fast forward to today I now have 47,000 plus miles of hard street driving (if that posible with this car) and no issuses. I do have the valve train noise which I feel is normal in these cars and will lose 1/2 a QT of oil on a good track day.

To sumerize: 25,000 miles @ 560 RWHP tracked at least 20 times, 15 of those with the SS vavle fix (if you want to call it that). this winter Katech will most likly do a short block and WCCH will get my heads for a freshing up. The reason... preventitive maintenance. I think Katech rebuilds race engines at around 20 hours of hard use, I think I have that.

Oh yes... I have always felt the oil was a little light, I have used the M1 with a zinc additive. Thinking Amsoil after rebuild, but most likely will follow Jason and crews advice.

Targeting 600RWHP with gen III cam next time around.... I think.

Hope this helps!

Originally Posted by 20psirabbit

Not to ask a dumb question, maybe I'm missing something-
I saw an earlier post on this thread where a member showed some unacceptable wipe pattern from the rocker to the valve.
Is there any chance that the heads weren't checked (either at all or to some standard) when assembled for good solid wipe patterns, leading to random guide wear and random valve failures from some having better wipe than others, so some wear quicker and more aggressively than others? Especially when the exhaust valves are the ones that are offset? Wouldn't something like that at least explain why there's not really a pattern to the failures?

Originally Posted by ZeeOSix

If you are talking about at the engine factory, then I'd have to say that no they do not check each and every valve wipe pattern. My guess is they never check it during engine assembly. Once the design of all parts is done and ready for manufacturing, GM counts on all the parts to be made per spec. At the assembly stage, the engine is basically assembled without detailed spec checks like rocker arm wipe patterns, etc. That has all been considered in the parts specs so that when all the parts are assembled they are supposed to fit together as designed.

If incorrectly machined heads (or any other part that was made wrong) makes it past any QA checks along the way, then they get assembled onto an engine which can obviously lead to major issues down the line.

Originally Posted by AirBusPilot

http://forums.corvetteforum.com/c6-z...-restored.html

I've always suspected it was a quality control issue, not a design flaw.

Bad news is that just replacing the guides with bronze and ss valves won't fix the root cause.

Originally Posted by '06 Quicksilver Z06

Looks like he sold this bad boy two days later.

http://forums.corvetteforum.com/c6-c...-2008-z06.html

http://forums.corvetteforum.com/off-...e-history.html

I guess he wasn't willing to find out if his new heads were milled right. I wonder why he deleted his response below Planet Zoom's.

Originally Posted by musicmankeb

Date of heads pulled: 7/5/12
Head Type: GM LS7
Year: 2006
Miles: 16,000
Track time: None
Tune: Stock
Mods: Haltech M103 + B&B exhaust for maybe 6,000 miles. Just put headers on the car within 300 miles and have been easy on the throttle since no tune. Car is currently at Katech getting stage 2 and these were the specs of the guides.

Gauge Valve diameter .3135"

Guide Clearances

Intake #1
Top .0027
Mid .0021
Bot .0024

Intake #2
Top .0030
Mid .0022
Bot .0028

Intake #3
Top .0025
Mid .0022
Bot .0023

Intake #4
Top .0030
Mid .0023
Bot .0025

Intake #5
Top .0033
Mid .0022
Bot .0027

Intake #6
Top .0028
Mid .0022
Bot .0025

Intake #7
Top .0029
Mid .0023
Bot .0027

Intake #8
Top .0030
Mid .0023
Bot .0028
=========================
Exhaust #1
Top .0022
Mid .0026
Bot .0069

Exhaust #2
Top .0022
Mid .0024
Bot .0048

Exhaust #3
Top .0020
Mid .0028
Bot .0064

Exhaust #4
Top .0022
Mid .0024
Bot .0039

Exhaust #5
Top .0021
Mid .0029
Bot .0085

Exhaust #6
Top .0021
Mid .0023
Bot .0046

Exhaust #7
Top .0021
Mid .0024
Bot .0054

Exhaust #8
Top .0022
Mid .0025
Bot .0033
=================

My observation, the exhaust valves on the left side of the engine (drivers side) 1,3,5,7 have more wear then the right side of the motor. Which makes me think oil could be a factor since that is the side furthest away from the oil sump. Regardless, every guide is out of spec on the bottom side of the guide. For a 16,000 mile car, this wear is not normal and I was told by Jason to replace all the guides and valves.

I also want to say to everyone who forgets this, some bronze guides will wear out faster then the factory powdered metal guides. Bronze is a softer metal and the factory powdered metal guides will actually last longer then bronze, ask any reputable shop.

My car is at Katech and is finished and is Katech #60 with a Stage 2 package with (bronze guides unfortunately), new OEM exhaust valves, and Katech Intake valves. I will have it back soon finally but feel like I regret the whole thing except having a 1 year 12k mile warranty. If I could do everything all over again, I would have done it myself and bought Mast heads because I do believe that there is some type of issue with these factory LS7 heads.

Just think about this for everyone who has had valve guide wear and had there guides replaced and or valves. You are not fixing anything, what is stopping your guides/valves from wearing down again. All you did was replace something that was worn, not fix whatever the problem is.

I'm not offering anyone a fix to this problem because I don't know what it is, just numbers and my opinion, you can take it however you want. I just hope this gets addressed someday soon!

Originally Posted by jvp

I had a chance to chat with one of the engineers at Carlisle about this specific issue. The discussion was fairly focused, and out of it I got the following points (paraphrasing, so forgive me here) ...

• It sounds like it's affecting a reasonably small number of '09, '10, and '11 Z06s. It's not the cause of any issues that have popped up with the LS7 in prior MYs.
• GM discovered the problem through their cylinder head warranty data; it went from nearly 0 to a peak of 6.5 problems per thousand engines.
• They inspected the returned heads and found the machining error in the valve guide. It had occurred at their head supplier. As stated in the thread already: it's not a design issue.
• Problems contained as of Feb '11 with 100% inspection of all heads.
• The most common customer complaint has been excessive valve train noise and if left unattended, an engine failure would likely occur. A handful of engines have been replaced under warranty due to these specific failures.

Overall, the engineer wanted customers to: enjoy their cars! If a problem is going to happen, it'll be accompanied by a nasty/excessive valve train noise long before the engine fails. He didn't quantify what "excessive" valve train noise means, as opposed to the LS7's normal ticking. I haven't had an LS7-equipped Vette in over 3 years, so it's been a while since I've last heard one. Pay attention to what your engine is telling you regarding its noises, but don't drive around like you're sitting on a time bomb.

jas

Originally Posted by jvp

I had a chance to chat with one of the engineers at Carlisle about this specific issue. The discussion was fairly focused, and out of it I got the following points (paraphrasing, so forgive me here) ...

• It sounds like it's affecting a reasonably small number of '09, '10, and '11 Z06s. It's not the cause of any issues that have popped up with the LS7 in prior MYs.
• GM discovered the problem through their cylinder head warranty data; it went from nearly 0 to a peak of 6.5 problems per thousand engines.
• They inspected the returned heads and found the machining error in the valve guide. It had occurred at their head supplier. As stated in the thread already: it's not a design issue.
  
• Problems contained as of Feb '11 with 100% inspection of all heads.
• The most common customer complaint has been excessive valve train noise and if left unattended, an engine failure would likely occur. A handful of engines have been replaced under warranty due to these specific failures.

Overall, the engineer wanted customers to: enjoy their cars! If a problem is going to happen, it'll be accompanied by a nasty/excessive valve train noise long before the engine fails. He didn't quantify what "excessive" valve train noise means, as opposed to the LS7's normal ticking. I haven't had an LS7-equipped Vette in over 3 years, so it's been a while since I've last heard one. Pay attention to what your engine is telling you regarding its noises, but don't drive around like you're sitting on a time bomb.

jas

Originally Posted by jvp

[*]They inspected the returned heads and found the machining error in the valve guide. It had occurred at their head supplier. As stated in the thread already: it's not a design issue.

Originally Posted by jvp

I had a chance to chat with one of the engineers at Carlisle about this specific issue. The discussion was fairly focused, and out of it I got the following points (paraphrasing, so forgive me here) ...

• It sounds like it's affecting a reasonably small number of '09, '10, and '11 Z06s. It's not the cause of any issues that have popped up with the LS7 in prior MYs.
• GM discovered the problem through their cylinder head warranty data; it went from nearly 0 to a peak of 6.5 problems per thousand engines.
• They inspected the returned heads and found the machining error in the valve guide. It had occurred at their head supplier. As stated in the thread already: it's not a design issue.
• Problems contained as of Feb '11 with 100% inspection of all heads.
• The most common customer complaint has been excessive valve train noise and if left unattended, an engine failure would likely occur. A handful of engines have been replaced under warranty due to these specific failures.

Overall, the engineer wanted customers to: enjoy their cars! If a problem is going to happen, it'll be accompanied by a nasty/excessive valve train noise long before the engine fails. He didn't quantify what "excessive" valve train noise means, as opposed to the LS7's normal ticking. I haven't had an LS7-equipped Vette in over 3 years, so it's been a while since I've last heard one. Pay attention to what your engine is telling you regarding its noises, but don't drive around like you're sitting on a time bomb.

jas

Originally Posted by LFZ

Thanks for your post and sharing that information. The part in bold, however goes completely against the beliefs of this forum. Interesting...

Originally Posted by jvp

I had a chance to chat with one of the engineers at Carlisle about this specific issue. The discussion was fairly focused, and out of it I got the following points (paraphrasing, so forgive me here) ...

• [*]
• [*]
• [*]
• [*]
• [*]

Overall, the engineer wanted customers to: enjoy their cars! If a problem is going to happen, it'll be accompanied by a nasty/excessive valve train noise long before the engine fails. He didn't quantify what "excessive" valve train noise means, as opposed to the LS7's normal ticking. I haven't had an LS7-equipped Vette in over 3 years, so it's been a while since I've last heard one. Pay attention to what your engine is telling you regarding its noises, but don't drive around like you're sitting on a time bomb.

jas

Originally Posted by AirBusPilot

Reasonable compared to what, prior model years? All LSx based engines?? Statistically insignificant???

Originally Posted by jvp

I had a chance to chat with one of the engineers at Carlisle about this specific issue. The discussion was fairly focused, and out of it I got the following points (paraphrasing, so forgive me here) ...

• It sounds like it's affecting a reasonably small number of '09, '10, and '11 Z06s. It's not the cause of any issues that have popped up with the LS7 in prior MYs.
• GM discovered the problem through their cylinder head warranty data; it went from nearly 0 to a peak of 6.5 problems per thousand engines.
• They inspected the returned heads and found the machining error in the valve guide. It had occurred at their head supplier. As stated in the thread already: it's not a design issue.
• Problems contained as of Feb '11 with 100% inspection of all heads.
• The most common customer complaint has been excessive valve train noise and if left unattended, an engine failure would likely occur. A handful of engines have been replaced under warranty due to these specific failures.

Overall, the engineer wanted customers to: enjoy their cars! If a problem is going to happen, it'll be accompanied by a nasty/excessive valve train noise long before the engine fails. He didn't quantify what "excessive" valve train noise means, as opposed to the LS7's normal ticking. I haven't had an LS7-equipped Vette in over 3 years, so it's been a while since I've last heard one. Pay attention to what your engine is telling you regarding its noises, but don't drive around like you're sitting on a time bomb.

jas

Originally Posted by beden1

as evidenced by their raiding the parts bin and offering a clone ZO6 in the Grand Sport model, will keep me from coming back anytime soon.