RAGGDOLL

Any of you guys frequent the C6 Z06 Discussion page?

Man, every other topic it seems is doom and gloom about heads and worn valve guides. I don't even like going there anymore...

walleyejack

If one absorbs all the input, 1 in every 2 would have problems. I think it is blown out of proportion. I know guys that had and have them with no problems. I wouldn t hesitate to own one.
if you want to dump it mike, i can take it off your hands to help you out.

SpartaGus

I've been staying away from the C6 Z06 forum for the last month or so. Every time someone buys a Z you get a lot of members saying get your valve guides checked! All the threads on the issue drive me nuts. I went out and extended my warranty GMPP Total plus. I'm covered for pretty much everything. Regardless of the guide issue, I was going to extend the warranty anyway! Good for the next 4 years.

After reading many threads on the issue I'm thinking it's geared more towards the 06 to 09 years. Maybe because more Zs were produced? And then we have the wiggle test method. How accurate is it? (Not all) but people have done it, got a out of speck reading pulled the heads off and they were actually fine!
The next four years while I have the warranty will be interesting, between Gm getting back to customers about the issue to customers launching law suits. Let's see what happens!

CDN_Wolf_eh

I would think that if you are planning on doing lots of track days (Road Course / Straight Line) ... you might as well get it done, and save the hassle down the road.

Kind of like the oiling system for 2006 - 2009's for Road Courses with high G load left hand corners (Like Mosport)


Mark

cdngolfer

I had my 08 heads done 2 years ago by DaSilva and don't worry about it anymore.

Pressman

I'm in the same boat as you. 4 years of warranty left - waiting and watching. Would like to hear what others in the area have done, as the Z06 page is rather scary.

RAGGDOLL

I think it's totally overblown. Talk to any reputable car guy/shop outside of the forum and no ones even heard of anything.

It just sucks because I used to spend a lot of time in C6Z. Now, a newb posts about how he just got his dream Z and guys automatically jump on them about heads

walleyejack

vt65

well i'm looking at an '07 with 70k on it and will get them done as the warranty is long gone so for 3G's it's cheap insurance, always liked the Z's and looking forward to adding one to my stable, it will help take the load off the '65 ...

by the way if anyone knows of a nice one for sale please give me shout..Rob

walleyejack

Mike. Sent u pm.
Al

MOSPORT1

just reading this info,,,


LS7 valve guide news.


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.

cdngolfer

Thank you!

There is some gratification in that I had the heads done on my 08 which falls within the problem window.

tlaselva

You have a 500+HP engine, running over 7K redline.

Car's get driven hard, then people cry when they're not as reliable as a 4 cylinder Honda.

That LS7 is a race engine, masquerading as a street engine.

People that expect a high performance engine such as a LS7 to not have the occasional failure, especially when they're driven hard, need to get their head out of they're sphincters.

When you buy a engine, you can have 2 outa the 3 things.

1) Cost
2) Reliability
3) Performance

We all know the LS7 is Cost and Performance.

If you want Performance and Reliability, go buy a Porsche, and even then there is no guarantee.

If you want Cost and Reliability, go buy a Toyota.

You CANNOT have all 3.

Monte04ss

The way I look at it, its cheap insurance to get the heads done.

Then drive the car, that is what it's meant for. It won't appreciate in value sitting in the garage.

Just received my heads from American Heritage Performance, should have them on the car in a few weeks.

I agree the Z06 forum is really doom and gloom, it used to be full of good info, now it take to long to shovel through all the BS

you gotta pay to play !

roysvette

C7 forums just the same. More problems than not! Phew, glad I got the only perfect problem free Stingray out there Mike.

American Heritage

The issue concerning the LS7 valve guide clearances is real and is not overblown by the forums (yes the c6z section has its "challenges" to wade through in order to get real world applicable info). The wiggle test is a go or no go test, plain and simple. All this back and forth over the accuracy of the wiggle test is way overblown. It either wiggles to much or it doesn't.
Compare a video of a 160,000 mile LS1 head:

vs a low mile LS7 head:


makes very little difference how you conduct the wiggle test. If its out it will be obvious. sure you can force the valve and get a different reading but not enough to make a big difference. If its out, its out.
What one chooses to do with their engine is their business we are just here to help those that would like help.

some are so bad you don't need to do a wiggle test:

nuck

Overblown perhaps because most cars aren't affected but a known problem that can take that expensive engine out has to be addressed. I wish it wasn't an issue but I can't fault people for talking about it. Its like the column lock thing with the C5s except potentially so much more destructive.

So we do the fix and then avoid the valve threads To those that haven't fixed it yet do the cam at the same time. The car needs a bit more jam to hang with the same marques it did when the ls7 first came out anyways.

walleyejack

oh they are all the same, my C6, terrible, have to put gas in it, change the oil, add air to the tires. just disgusting

LS7 BUD

Every single year of C6Z has had a valve drop... Don't think for a second they even fixed it lol... Had a buddy pull his 2013 C6Z heads after 6,000km and the guides were worn... I've personally have had a valve drop and wipe out my motor... I paid outta pocket... Don't ignore the fact there could be something wrong... Every single new owner of a C6Z should have their heads check... All the people who disagreed with me back in 2011 have either had a valve drop themselves or have had their heads fixed...

RWspinning

so the cherry has been popped on my former car? damn I miss that car, and that exhaust burble and the rush you get while just driving around. any pics of how she stands now?