double06

This was one the LS7 Engine in Z28 Camaro on the Camaro Homepage.com. Tells about development n 2003-2005 but also some recent stuff in 2010-2013. Not sure if link works but enough there to find it. Some interesting 2005 story about the bay to bay breathing windows adding 10-15 hp (originally had none) and getting them to the 505 hp mark.

www.camarohomepage.com/ls7/index.htm

Jawnathin

Thanks for sharing again. Hib Halverson the author is also a forum member here. There was Corvette article too, which had largely the same contentpictures/info, just a few tweaks for the Corvette platform.

So glad it was a 7.0L instead of a 6.4!

Matt Cyber Z06

We asked Dennis Gerdeman, if he could revisit the LS7 head design, today, what he'd do differently. "From an analysis standpoint, our tools have improved significantly over what we had back when we developed this cylinder head," Gerdeman replied. "I would probably play with valve sizes, again, and locations within the chamber just to see if there's a little more we could squeak out of this from an airflow perspective. I don't think it would change significantly, but we may have ended up with a little larger exhaust–maybe a slightly smaller intake. It may even have led to a slightly different intake port shape with a different area schedule.

"Those are probably the two things I'd like to revisit: the intake port and small tweaks to the valve sizes or centers, because with the tools we have today, you can accomplish that in hours instead of weeks. Before you had to make a CAD model, send it to a job shop and have them cut you a flow box then, flow it on the bench and try again. Now we can do it with analysis in a fraction of the time."

-

The above statement was Comforting lol

JohnRR

Double06, thanks for sharing that article on the LS7 development.

John

rockinSeat

Look for an updated version of the article coming out soon...oh it's there, check out pg 17.

http://www.corvetteactioncenter.com/...l#.Uv2kqn-9KSM

JwT

Holy Cow Batman!!! Did GM just say that machining errors on the LS7 heads have caused engine failures? Hummmm sounds like the same thing that people have known for some time here on the forum. I wonder how many heads that have been replaced have the same issue.

It's really thoughtful of GM to say that if your out of warranty the cost is on you. What a bunch of slimey S.O.B.'s. Yeah we have a problem yes the fault is ours but if your out of warranty screw you!! And by the way when we do replace the heads on those with a warranty we destroy them asap to hide the problem.

I guess all the people here who called us chicken littles and still do have some.... Splaning to do Lucy. This looks like good lawsuit material to me. I really don't feel so bad about buying my PRC's now. Thanks for the post Rockin.

Mark2009

There is nothing new in what you read, some of it appears to speculation that you seem to have confused with fact (head destruction), and some of it is wrong.

JwT

What are you talking about Mark? It's new to me. You act as though GM came forward a long time ago and told everyone hey we have a problem and were going to correct it. They didn't....and in fact mislead the public and Z06 owners that there was no issue at all.

The only thing I'm confused about is where is the speculation? I wasn't aware that you had it all figured out. Perhaps you were there when the errors occurred....but I doubt it. You should contact the Corvette Action Center and tell them the error of their ways and demand a rebutal.

Until then, the things that you seem so aware of are just...Speculation.
While I certainly don't believe everything I read there seems to be truth in the article. And even though you come across as the wizard of the Z06 and do not respect anyone else's opinion on the subject, I do respect most of yours. People were and are being wronged by GM's lack of empathy towards their defective product. And while there may be a difference of opinion about the cause the fact that anyone without a warranty is pretty much S.O.L.

Mark2009

Your level of awareness is not my concern unless/until it reaches the level of misleading others here.

The incessant whining about the issue needs no comment/rebuttal since that seems to be a central pastime for many in our society these days.

JwT

It's sad really, your a piece of work you know that. You and your no-misleading comments. A perfectionist for the truth. I know, I know GM would never mislead the public. And that incessant whinning your talking about, tell it to the people that have been dicked to the tune of 14k.......but that's not you is it? You stand high on your mountain of Truth, Justice and the American way. I remember you back when you stood on your platform and shouted to the world that there was no issue. But all that changed one day.....now your the champion of the new truth. But back then it wasn't......hummmm

Don't worry whenever you puke you judgemental garbage some people will still be right behind you saying.....

Mark2009

Lying enhances neither your credibility nor your argument.

JwT

Come on buddy....everyone knows your the only one with credibility here. Are you stating that you never said there was (no issue) with the heads on the LS7....? Love ya bunches....

Norm_427

http://www.corvetteactioncenter.com/...l#.Uv5DqHkVKfE pages 17, 18

I'm copying this for the sake of convenience. Emphasis added is mine.

Oops...In Spite of Best Laid Plans

In any car company's manufacturing process, a weak link can be parts suppliers. Not only General Motors but Ford, Toyota and every other car company has to deal with this situation. An engine manufacturer can have the world's best design, but all it takes to turn the situation FUBAR is one supplier's quality control to slip. Worse yet: if it's problems downstream in a supply chain-say the quality control of a source of materials (such as: a bearing maker) to a manufacturer which supplies parts (such as: rocker arms) to a final assembly facility (such as: GM's Performance Build Center)-the result can be quite unfortunate. Sadly, this happened twice in the LS7s life.

The first problem developed in a relatively small number of LS7s assembled during the first half of 2007. In late 2006, about 1500 rocker arms were manufactured by GM's rocker arm supplier using defective needle bearing assemblies made by that supplier's source for bearings. The end caps of these defective bearings could fracture at the radius between the side and the top of the cap. When that happened, the top, or pieces of the top, separated from the rocker arm. Once the cap failed, bearing needles exited the rocker. The cap fragments and/or needles would either lodge in cavities in the top of the head or be flushed through the oil return holes in the head and down into the oil pan. The oil pickup screen is too fine for these pieces to get sucked into the oil pump, so they would reside in the oil pan until the next time the oil pan drain plug was removed. When the rocker am bearing retainer fails it may fracture in several places.

When an LS7 rocker's bearing retainer fails and all the needles are ejected, the engine makes a lot of noise and valve damage is likely.
In some cases, the problem can be worse than just needles in the drain oil. If a full "bearing load" of 33 needles gets loose, significant play develops between the rocker fulcrum and the rocker body with engine operation quite noisy. If the engine runs for an extended period with such a large large amount of play in the rocker arm, damage to the valve, the valve locks, the retainer or all three may occur. Damage to those parts may allow a valve to drop into the cylinder. The result of that is catastrophic failure of the engine.

A small amount of LS7s, assembled between early January and late July 2007, were had these defective rockers. Most have been repaired under warranty, but even today, there are occasional reports of '07 LS7s with needles in their drain oil. With '07s now out of warranty, repair of an LS7 with failed rockers will come out of the owner's pocket. If you find rocker roller needles in drain oil, immediately inspect all 16 rocker arms and make repairs as necessary because, if you don't address that problem quickly, dealing with it later may cost you far more.


The second anomaly was excessive valve guide wear and was a problem with a few 2008 to early-2011 engines. The problem manifests itself as excessive valve noise combined with high oil consumption. If not addressed when it's first discovered, it can result in engine failure.

The "LS7 valve guide problem" has been the subject of thousands of posts to Corvette-related forum web sites dating back to the late-'00s. By 2011, even if you discounted a substantial amount of the traffic as posted by trolls, conspiracy theorists and uninformed whiners, it was clear that some LS7 owners had trouble with valve noise and oil consumption and were incensed by what they believed was General Motors' lack of appropriate response to their concerns.

GM eventually acknowledged the controversy in 2012. According to statements made by GM engineers to attendees at the "Corvettes at Carlisle" event that summer and statements posted on forum sites by Chevrolet Customer Service in the fall of 2012, the condition was discovered during an investigation into warranty claims involving cylinder heads. The volume of problems with heads spiked from practically zero to a high of 6.5 problems per 1000 engines. Chevrolet Senior Customer Relationship Specialist, Evan Sawaya, said in web forum posts, "Through inspection of returned heads, it was determined that a machining error in the valve guide had occurred at our head supplier." The problem was solved in February of 2011 and the solution verified with valve guide inspection of 100% of heads manufactured from that point to the end of LS7 production.

In mid-January, 2013, GM issued a "technical service bulletin" (TSB) to dealers which stated that GM’s warranty numbers for LS7 valve and head replacement, “...are very low with no indication of an excessive wear issue.” While that conflicts with anecdotal information posted to web forums along with what Chevrolet Customer Service stated in the Fall of 2012, the TSB goes on to instruct dealers that, if a customer has a documented problem with valve guide wear and the warranty for his or her Z06 is still in force, the engine should be repaired at GM's expense. We asked General Motors to elaborate on the TSB, but it declined to comment further and referred us back to the Fall 2012 statements made to the Corvette Action Center and other forum sites by Chevrolet Customer Service.

One or both of two cylinder head machining errors would cause rapid valve guide wear: 1) valve guide centerlines not machined concentric with valve seat centerlines and 2) guide centerlines not perpendicular to the valve seats. Either of these characteristics would cause rapid guide wear, abnormal valve noise, increasing oil consumption, and eventual engine damage.

It's likely that not even General Motors knows the specifics of the machining error because, in any warranty return head where an excessive rate of valve guide wear took place, the "evidence" would have been destroyed. There would be no way to quantify the relationship of the original centerline of a badly worn valve guide to the centerline or plane of its valve seat. So...how did GM arrive at a "machining error" as the probable cause? Understanding the cylinder head design and its manufacturing, we believe it possible that the cylinder head suppler, Linamar, determined the cause though an internal investigation then advised GM of its findings.

It is unknown how many cylinder heads had this problem, but we suspect it was a modest number. Our advice: if your LS7 makes excessive valve noise and has what you feel is high oil consumption, take immediate action. If your engine is still under warranty, take your Z06 to your GM dealer and explain your concerns. If the dealer can confirm the problem, it's likely GM will repair the engine, however, the above mentioned service bulletin, also, implies that, if your engine is modified, GM will likely not accept a warranty claim, no matter how severe the guide wear might be.

If your engine is out of warranty, visit a Chevy dealer for assessment of the problem but know that any repairs will be at your expense. If you're a do-it-yourselfer or you are having an independent service facility assess your
engine's condition, the procedure with which one can measure valve guide wear is covered in the "Engine-Mechanical" section of the Factory Service Manual. There are explanations of the measuring procedure posted on the Internet and some of those posted procedures are incorrect. Do not use any checking methods other than those prescribed in the Service Manual otherwise the measurements will be inaccurate.

ATC399

Nice article thanks for posting OP

Matt Cyber Z06

Thanks Norm, Good idea

rockinSeat

I've been working with the author a bit for the past couple of months, pushing for more research and answers. There should be a revised version of the article with more research about the guides in about three weeks or so.

Agreed a lot of material in there right now is not new to those of us that follow the issue religiously, but I think there will be more to come.

Obviously the problem with the ls7 valve issue has been that everything is speculation, but when you have a real journalist interviewing real engineers at GM, there is some credibility there.

Ultimately, as owners we need to make our own decisions.

JetBlue427

"Chevrolet Senior Customer Relationship Specialist, Evan Sawaya, said in web forum posts, "Through inspection of returned heads, it was determined that a machining error in the valve guide had occurred at our head supplier." The problem was solved in February of 2011 and the solution verified with valve guide inspection of 100% of heads manufactured from that point to the end of LS7 production."

what? Evan has a last name and is actually real...some people were trying to make me believe he was a troll who just made all that crap up

Matt Cyber Z06

Ok... This is something we knew but--

Lets try this, Have a "Registry" made up of either 2012+ LS7's and Warranty exchanged Heads LS7's from the Dealer.

Basically, All the 2012 model C6Z's and the People who went to the Dealers and they Warranty exchanged there Heads.

forg0tmypen

Very interesting read!!

Hib Halverson

I'm the guy who posted the LS7 articles at the CAC. I'm, also, the one "rockinSeat" speaks of in post #16 above.

There is a project underway to revise that article and it's a direct result of the situation with premature valve guide failures in LS7 cylinder heads. The CAC's webmaster, Rob Loszewski and I are doing the revision in phases. In fact, "phase," two small updates, was posted about week ago.

"Phase 2", a much larger section of revised material and some additional imagery, is just about ready to go up. Last Thursday, I completed the last of several interviews with various sources around the country familiar with the problem. There is one outstanding fact check to complete and then, unless I've screwed up on that one issue, we can post the phase 2 revision.

"Phase 3", a detailed explanation of "wiggle testing," including imagery, along with an opinion piece, both posted as sidebar articles, will come next. They are underway, but probably a month out from being posted. The wiggle testing procedure is quite difficult to excecute properly and that's why it's taking a while to do the shop work, shoot the images and write the article.

"Phase 4", is only tentative and in the planning stage. It will cover how to built the "ultimate" LS7 cylinder head for the 600-625 hosepower range using production castings. In this case "ultimate" means performance, reliability and durability. If phase 4 happens, it will also be presented as a sidebar.