LS7 Valve Train Questions/Concerns

[COPO-RAT]

Ok guys, my brother-in-law has an '06 Z06 (LS7) and has recently become concerned about valve train issues with the LS7. He has heard that some of them have a machining issue that causes a valve to drop. I've also heard of valve spring failures on early '06 models. Is there any validity to either of these concerns? The car has 23K miles on it and it is NOT a daily driver. Will most likely never see a road course or autox, he just enjoys driving it spiritedly on the windy mountain roads of Eastern KY.
He is considering a Stage 2 upgrade from Proheads.com to gain some power and alleviate any possible problems that may be lurking. He has also been told to go to Brian Tooley for head work. Anyone have any experience with either of these places? Any suggestions?
Thanks in advance!!

[6fastback7]

Some guys have driven almost 200K miles on the stock motor with zero issues....some have went 10K and dropped a valve! there really is no honest reason as to why...and we have the top shops in the country trying to figure it out. 50% of the shops will say to replace the sodium filled valves...the other will say there just fine! I honestly dont know what to believe anymore. West Coast Cylinder heads is one of the most respected LSX head guys out there and he replaces the valves with SS solid valves and bronze valve guides. Now Katech (probably the leader in LSX engines) says dont change the valves and if your worried then rework your heads and replace the valve guides. The confusing part is...guess who rebuilds all Katechs heads...West Coast! So if you want my opinion...no one knows the answer! at least not yet
I am sure GM probably has more answers then anyone...but my opinion is they will just replace the motors under warranty till this problem is no longer on there books...and since this is the last year for LS7..that means 5 more years of warranty and there off the hook!
But the LS7 is definately not bulletproof...we have only a small percentage of the 30K owners on board...and have documented over 50 failures for various reasons...and who knows how many more have failed that dont cry about it on forums?

[68sixspeed]

Pretty much right on the head there.... If he isn't covered under an extended warranty, I would suggest checking the guide wear over the winter which can be done in the car. The jury is still out in the 1pc stainless vs stock valves and also how fast the bronze guides will wear out compared to stock. I'm going to give it at least 6 months to see what shakes out.. The info really just came out over the summer on the valve problem so I don't think anyone knows for sure how to fix it or the root cause of the rapid guide wear. Some cars have it, some don't so far. Perhaps some aftermarket castings will be the better fix... I think it is too soon to tell.

[6fastback7]

I see you have 2 LS7`s...what kind of mileage and abuse do you have on them? I have a garage queen..sunday cruiser with 10K (no track miles, no 1/4miles) and babied other then about a dozen or so rumps to the redline after i bought it. Part of me wants to rip the heads off just cause my car would be a perfect example of premature valve guide wear...if i actually do have any wear at all.

[Ron.in.SoCal]

JMHO, I don't believe there is a design problem that can be proven. The number of failures vs the total 06-07 LS7s is what, 1%? 2? 4? Who really knows? Certainly more than a few guys have dropped a valve and are very vocal about it. I've done the research, read all about it on the vette forum, am totally confused about what the problem is and appropriate remediation. I even asked my well respected engine builder if bronze valve guides could be the cause and he said no way.

I hope none of you guys have any problems drive it till the wheels fall off...:lol:

[68sixspeed]

I see you have 2 LS7`s...what kind of mileage and abuse do you have on them? I have a garage queen..sunday cruiser with 10K (no track miles, no 1/4miles) and babied other then about a dozen or so rumps to the redline after i bought it. Part of me wants to rip the heads off just cause my car would be a perfect example of premature valve guide wear...if i actually do have any wear at all.

The z06 has ~16k miles on it, mostly street, 1 or 2 drag race days and only 4 or 5 HPDE days but those usually have 100 track miles per day. I am pretty easy on it on the street, waiting for oil temp before getting on it etc and maybe running out 1st and 2nd gear a couple times when I'm out. I'm getting old and boring I guess. Since this car has GMPP warrantee for 2 more years I'm leaving it bone stock and not touching anything until that is up.

The camaro's motor is out of a 2007 with 7 or 8k miles on it when I bought it. I checked the guides when I did the cam and spring swap and they felt good, maybe .003/.004 on two of the exhaust valves with the valve open, the rest were all ~.002 just going by feel. I've put around 1k miles on it so far, I'll probably check the two that were were worn more over the winter. If I'm going to have a problem I'd expect it here with this motor with the cam and I tend to have more "fun" with the cheap rear tires on this one. Great 2nd gear burnouts. 533rwhp and 508 on torque is also more stress on it than stock.

It seems that if an LS7 is going to fail, it is from 2 main areas, running out of oil which was fixed with the larger tank in 08 or 09, not an issue on street tires though; or dropping a valve. I agree it is probably a 1 or 2% kind of thing but still higher failure rate than say the old z06's LS6 which were pretty tough. Every motor has a weak spot, it's just how to address this one isn't fully known yet. I'm tempted to look into aftermarket heads when the time comes, but I want to give the topic some more time and just watch the valve guide wear until then.

[John@Texas-Speed]

As far as the valve goes it has been proven that the stock 2 piece exhaust valve is the problem. The tip comes apart and drops into the motor causing the failure. We have seen that the stock guides will wear out very quickly. We find ourselves replacing those quite often when porting customer stock casting heads. All of our aftermarket castings get bronze guides. Both of these issues can be fixed with aftermarket parts pretty easily, buts its impossible to tell when its going to happen on a stock motor.

[COPO-RAT]

Thanks a TON for the info/insight guys. I'm pretty sure he is convinced that he is sending the heads out for work. I guess the possibility of there being a problem opened the door for him to have some mods done! :headbang:

For those of you interested, check this thread out!

http://m.corvetteforum.com/c6-z06-discussion/3138605-20k-miles-valve-guide-specs.html

[6fastback7]

Thanks a TON for the info/insight guys. I'm pretty sure he is convinced that he is sending the heads out for work. I guess the possibility of there being a problem opened the door for him to have some mods done! :headbang:

For those of you interested, check this thread out!

http://m.corvetteforum.com/c6-z06-discussion/3138605-20k-miles-valve-guide-specs.html

there is a thread like that once a week...its no fun loggin into CF anymore...but as far as modding goes...i have zero confidence in trying to squeeze more power out of that bottom end. Katech recently said that they have seen cracked pistons causing the valves to break...of course that opens the big debate all over again. But there was also another thread where a member had a conversation with one of the corvette engineers on what a safe power would be once you start modding...his answer was not to try squeezing anymore out of this motor..he said they built this LS7 to the limits they could safely make it reliable. So modding the heads...then swapping a cam and tune...may make the top end more reliable but it doesnt solve any potential bottom end problems.

[parsonsj]

I've been debating all summer on what to do with my Z06. It sees significant track time, and I'm all about using all the RPM that's available.

I've never seen a good answer to a fairly simple question: can the engine still turn 7000 RPM with heavier SS valves?

[68sixspeed]

I've never seen a good answer to a fairly simple question: can the engine still turn 7000 RPM with heavier SS valves?

WCCH (cyl head guru) says SS are fine, Katech says to stay with the GM valve.

I actually lowered the rev limiter etc on the camaro, with the Katech torquer cam, peak HP was around 6100-6200, I figure I don't need to spin 7000, hopefully extend my engine life.

[parsonsj]

WCCH (cyl head guru) says SS are fine, Katech says to stay with the GM valve. I know. I've spent hours reading the fora over at CF.com. And not to pick on you, but I'm not hearing the answer to my question: can the motor still hit its designed redline with SS valves? WCCH doesn't ever really answer that question directly.

[6fastback7]

I know. I've spent hours reading the fora over at CF.com. And not to pick on you, but I'm not hearing the answer to my question: can the motor still hit its designed redline with SS valves? WCCH doesn't ever really answer that question directly.

i dont think its a question of can it hit the rev limiter with SS...but more so...can it hit the limiter without floating! and I have no idea how WCCH decides when a setup is safe....I believe Katech uses a Spintron to monitor valve train dynamics and would trust there word more then Richards on what kind of punishment a valve and spring combo can take.

[68sixspeed]

JP, I'm in the same boat... Reading a bunch and trying to filter it out. My interpretation is that the 2 pc valve is not the root cause, but with worn guides may be more likely to drop. But no, I don't think anyone has a 100% yes/no on 7000 rpm with SS valves. Personally I think SS valves should work, I've built several gen 1 small blocks with the same or larger exhaust valves and huge heavy stainless intake valves, but they ran a lot more spring pressure and a mech roller cam, not hyd.... If Katech or someone has or would share SS valve spintron data or results with stock vs some other spring pack it sure would be helpful. I used their cam, spring, and Ti retainer setup on my 68's ls7 and I know that combo was tested on the spintron but with the 2pc exhaust valve.

I wonder what the actual weight difference is on the solid vs sodium filled 2pc valve? How much of that can be made up with changing to the Ti spring retainer?

[parsonsj]

I ordinarily give GM lots of leeway... they've got more and better engineers than anybody else. If GM thinks the 2 pc sodium filled valve with its smaller diameter stem is good for 7000 rpm, I give that a lot of weight. WCCH's use of SS valves strikes me as a bit of "one size fits all" thinking... they've always used those massive valves and so they should be good in the LS7 world too.

I thought the LS7 already used a Ti retainer... but I'm not sure.

Anyway, Katech's spintron data is also good evidence that the valve itself isn't the problem, but still... lots of opinions passing as facts out there.

I think I'll be pulling the heads on mine, but I'd like a plan of attack beyond that.

[68sixspeed]

Definitely steel retainers (& locks) on my motor. (Chased them with a magnet) My thought is that when the extended warranty on my z06 is up, the heads will be due if it hasn't blown up by then. Hopefully a solid proven fix is figured out by then, or I'll be sending it to Katech for a stage 2 package and maybe forged pistons too. I don't think their price for the stage 2 is bad w/o the corsa exhaust, new heads, cam, lsxr intake etc. ($6200 installed, tuned)

I am actually surprised wcch or others are not doing ceramic or other coatings on the exhaust valve to reduce heat transfer - pretty common practice on turbo motors etc. Of course if money is not an issue, go with coated Ti on the exhaust valves and weight is not an issue. (Until the guides wear out again)

--Dan

[6fastback7]

those who were following and have not seen the recent thread on the CF forum...GM has announced the following

Originally Posted by Chevy Cust Svc
Hello all,

LS7 Valve guide issue summary:
• Affects a small, number of '08, 09 ’10 and ’11 Z06’s
• GM discovered the condition through our cylinder head warranty data involving a very small percentage of our vehicles.
• Through inspection of returned heads, it was determined that a machining error in the valve guide had occurred at our head supplier.
• The quality issue has been contained as of Feb 2011 with 100% inspection of all heads.
• The most common customer complaint has been excessive valve train noise.
However if the condition is not addressed, it could result in engine failure. To date, where this condition has been observed, it has occurred early in the vehicle life.
What customers need to know: They should drive and enjoy their vehicles without fear. If their car demonstrates this condition, they are likely to hear unusual valvetrain noise first. If you have a concern regarding this issue on your personal vehicle feel free to contact me through private message on this forum and we will work to assist in resolving your concern. Feel free to contact me through [email protected] please put attention Evan in the subject. As always, vehicles that have modifications to the powertrain or the calibrations, are no longer covered by GM's warranty.

Sincerely,
Evan, Chevrolet Customer Service