Originally Posted by C6z06man

I hope GM plans on reimbursing those that spent money out of pocket for fixing the problem. My engine was a 12/08 build and could easily see the movement on a few valves with the spring still on.

Originally Posted by psp6158

Thanks for the information, although you say you learned some valuable information when they used the machine on your heads. Im curious what you learned and I've read what you posted several times, but I don't see what the results were (forgive me if I missed it) if they were out of spec, if they were within spec., did you just put them back on the car? I am in the same boat as many with an 08, failed wiggle test, out of spec upon measuring, they are admitting there was an issue during that time, with no cure... I'm praying this isn't a way for them to back out of paying for replaced heads based on a wiggle test that many professionals were using. I would think, that most reputable shops that used the wiggle test for a preliminary test, also got the measurements with a more precision with the heads off. (Like mine) I'm in the minority but can you tell us the other forum where we can continue to follow please, jeff, thanks again

Originally Posted by Bill Dearborn

If you have documented measurements showing your guides are out of tolerance why aren't you talking to GM? As I mentioned in the other post start with writing a letter to Mary Barra at GM explaining what is going on and what you want GM to do about it.

You will get a response. It will be Yes or No depending on what the data shows. Remember you don't walk into the throne room asking the King to be magnanimous while trash talking him at the same time.



Another key point about this kind of request. You don't start with the lowest Customer Service Representative in the company, you start with the highest one and that is why the letter is sent to Mary. That gets the attention of the person who has the power to change over rule lower level procedures and positions.

Bill

Originally Posted by Michael_D

All that to inform the public that "wiggle testing" is not accurate?? Duh. Many of us (who actually do know how, and actually do use precision instruments) have been saying that ever since that GM procedure was introduced. The only "new" news here, is that GM is saying it isn't accurate.

The test however, is still a damn good, and damn simple/quick way to check and find out if you have excessive wear, and if you should yank the heads off or not.

Whether or not some vendors and shops are dishonest and will take advantage of people is a completely different topic. That's the end user/owner's accountability. The accountability to educate themselves. Accurate???? NO!!!

Originally Posted by Michael_D

But good enough to be leading indicator of imminent failure?? YES!!

Originally Posted by Hib Halverson

Last week I was in Michigan for a day of meetings with various engineers at the General Motors Powertrain Division. Two of the meetings were about GM's two new premium V6 engines, the LGW and the LGX. The third concerned the LS7 valve guide wear problem.

Present for the LS7 meeting on the afternoon of 24 March at GM Powertrain Headquarters in Pontiac, were: Jordan Lee, Chief Engineer and Program Manger for the Small-Block V8, John Rydzewski, Assistant Chief Engineer for Small-Block V8 Passenger Car Engines, Chris Cogan, Cylinder Head Design Release Engineer for the LT1, LT4 and LS7 and Yoon Lee, LS7 Design System Engineer. Also present was Tom Read, Director of Communications for GM Powertrain. In attendance for part of this meeting were representatives from GMPT's Inspection Department, from Zeiss U.S. and the GM entity which complies service information.

This meeting included a visit to the Inspection Department at GM Powertrain HQ where I observed a Coordinate Measuring Machine (CMM) session with the passenger side cylinder head which was removed from my engine in July of 2014 during a warranty replacement. A CMM captures measurements used to create an extremely precise, three-dimensional, digital model of an object, such as an LS7 head. The GMPT Inspection Department uses Zeiss "Prismo Navigator" CMMs which are accurate to two microns over a distance of 300-mm ( .00008-in over one foot).

What I learned from LS7 Team at Powertrain will be incorporated into revisions to my series of LS7 articles which are posted on another web site. These revisions will take some time to produce. There is no posting date for them at this time.

There are some open issues remaining after this meeting and they will be explored via a follow-up exchange of emails I will be having with Tom Read and the LS7 Team in the next week or so.

At this point, I can reveal some news items which came out of that meeting. I'll cover them briefly, here, and will expand upon them, later, in my revisions to the LS7 article series.

1) "Wiggle Testing" at best is inaccurate and in many cases is completely unreliable. Observing one of my heads being measured by one of GM's Zeiss CMMs proved to me conclusively that even the complicated and careful procedure I covered in my Wiggle Test article produces data which is inaccurate and inconsistent such that, unless the clearance measured is significantly greater than the Service Limit of .0037-in., the measurements are useless for determining if a head needs repair or replacement due to valve guide wear.

2) It is possible that heads which had Wiggle Test results of more than .0024 (intake) or .0026 (exhaust) but less than .007-in. stem-to-guide clearances had actual clearances below GM's .0037-in Service Limit, regardless of how the Wiggle Test was done. That possibility becomes greater as Wiggle Test measurements get closer to .0037-in. Once they approach .005-in., guides are likely in spec even though they Wiggle Test as bad.

3) Some, but not all, heads which failed "Wiggle Tests" and were repaired or replaced, either under warranty or not, actually did not have faulty valve guides and did not need replacement.

4) Wiggle Testing is "out" at GM. In early March, GM released to its dealers an update to ESI mandating a new procedure for measuring stem-to-guide clearance for warranty purposes in all high-performance engines. It requires a hole gauge to measure guides and a micrometer to measure valve stems or a valve guide bore gauge, such as a Sunnun P310, and must be done with the heads removed and disassembled.

5) The demise of Wiggle Testing as a way to determine if guides are worn was a result of the LS7 Engineering Team's review of the LS7 article series, three CMM inspections of the heads removed from my engine in July of 2014 along with the Team's need for more accurate information from the field about warranty replacements of LS7 heads. Additionally, the LS7 Team's review of selected content on the CF, on another web site which also has a C6 Z06 forum and on additional web sites besides those two, may have influenced the decision.

5) According to Jordan Lee, the "machining error" stated here on the CF by Chevrolet Customer Service in October of 2012, was a failure of the supplier to properly deploy statistical process controls and, as a result, the diameters of valve guides in some, but not all, heads made during that period were machined too large.

6) The "suspect period" for this machining error, previously stated here on the CF and on other web sites by Chevrolet Customer Service to be 2008 to Feb 2011, is not correct. According to Chris Cogan, and confirmed by Jordan Lee, the suspect period was July, 2008 to March, 2009.

7) Only LS7 heads are manufactured by Linamar. LS9 cylinder heads were never manufactured by Linamar. LS9 heads were made in GM's engine plant in Silao, Mexico. I am partially responsible for that long-standing piece of misinformation. I apologize for any confusion it has caused.

8) The LS7 is currently manufactured at the Performance Build Center in Bowling Green and will remain so until the 5th Gen Camaro Z28 goes out of production.

I may post additional information concerning my 24 March visit to GM Powertrain as conditions warrant.

Thanks to the LS7 Engineering Team along with Tom Read, GMPT Director of Communications, for the time and resources they devoted to my visit with them in Michigan last week. I'd also like to thank the LS7 Team for their willingness to show me all the information they had available at the time of the meeting and their willingness to consider sharing additional information going forward. Finally, I appreciate the LS7 Team's interest in working with me to get as much information on LS7 valve guides as possible into the public domain.

Originally Posted by moose.b3

"According to Chris Cogan, and confirmed by Jordan Lee, the suspect period was July, 2008 to March, 2009."



So according to these dates, the only Z owners that should be concerned are 2009's and maybe some early 2010's. That's going to surprise a lot of people. Especially the owners of other years that dropped a valve. Must be all the internet hysteria going around.

Originally Posted by EWK

How do you determine the build date of the engine?
I have the 2009 with 7,666 miles on it that had every intake/exhaust valve out of service spec as measured by WCCH. My engine was still under the powertrain warranty and when I submitted my paperwork to GM Headquarters requesting reimbursement, even though they contacted Katech who did the actual mechanical work, GM denied my claim. The GM warranty representative even went so far as to remind me that "after all it is a used vehicle". I went to Katech because of the confidence level that came with their doing the work and their proven LS7 engine experience. Now I am curious about the build date.

Originally Posted by KGjevre

....

How to get your engine’s build date:
Look up the engine number (instructions here) and then post it to the same thread and someone hopefully will respond with the engine build date, or calculate it yourself from this info:
The engine number looks like this 10zld xLDDDxYBB
The second digit is the line number (L).
The 3rd, 4th, and 5th number is the day of year (DDD).
The 7th number is the year (Y).
The last 2 numbers are the engine built of the day number (BB).
To turn the day-of-year number into a date you can use this link: http://www-air.larc.nasa.gov/tools/jday.htm
.....

Originally Posted by Michael_D

All that to inform the public that "wiggle testing" is not accurate?? Duh. Many of us (who actually do know how, and actually do use precision instruments) have been saying that ever since that GM procedure was introduced. The only "new" news here, is that GM is saying it isn't accurate.

The test however, is still a damn good, and damn simple/quick way to check and find out if you have excessive wear, and if you should yank the heads off or not. Accurate???? NO!!! But good enough to be leading indicator of imminent failure?? YES!!

Whether or not some vendors and shops are dishonest and will take advantage of people is a completely different topic. That's the end user/owner's accountability. The accountability to educate themselves.

Originally Posted by JP426

Hib,
I thought you validated your wiggle test using the test indicator method by having measurements done by your machinist on your removed heads.
Is the test indicator method inaccurate also?

Originally Posted by moose.b3

"According to Chris Cogan, and confirmed by Jordan Lee, the suspect period was July, 2008 to March, 2009."



So according to these dates, the only Z owners that should be concerned are 2009's and maybe some early 2010's. That's going to surprise a lot of people. Especially the owners of other years that dropped a valve. Must be all the internet hysteria going around.

Originally Posted by '06 Quicksilver Z06

Bull****. Pure, wet, steaming and unadulterated bull****.

Point to the studies which demonstrate that it is a "leading indicator of imminent failure".

Originally Posted by moose.b3

"According to Chris Cogan, and confirmed by Jordan Lee, the suspect period was July, 2008 to March, 2009."



So according to these dates, the only Z owners that should be concerned are 2009's and maybe some early 2010's. That's going to surprise a lot of people. Especially the owners of other years that dropped a valve. Must be all the internet hysteria going around.

Originally Posted by 2k Cobra

If the wiggle test was no good, how come they approved paying for it if bad guides were found??

Originally Posted by propain

Point to the studies the grossly out of spec guides lead to valve failure? Really? I must not be reading this statement correctly. Are you suggesting the grossly out of spec guides are not an indicator of imminent valve failure if not addressed?

Originally Posted by moose.b3

"According to Chris Cogan, and confirmed by Jordan Lee, the suspect period was July, 2008 to March, 2009."

So according to these dates, the only Z owners that should be concerned are 2009's and maybe some early 2010's. That's going to surprise a lot of people. Especially the owners of other years that dropped a valve. Must be all the internet hysteria going around.

Originally Posted by Dirty Howie

Hib can you post any information about possible outreach from GM to the secondary market?
(snip)

Originally Posted by '06 Quicksilver Z06

Not saying that part in bold above at all.

How can an admittedly inaccurate test, a test which by definition would yield less than accurate results, reliably predict the imminence or impendence of any event, be it good or bad?

His comment was that this test was; "a leading indicator of imminent failure".

I'd like to see his proof of this claim.

Originally Posted by psp6158

Thanks for the information, although you say you learned some valuable information when they used the machine on your heads. Im curious what you learned and I've read what you posted several times, but I don't see what the results were (forgive me if I missed it)