CGZO6

Edit: Motor was a SEP12 build, well after the Feb11 100% inspection of all LS7 heads.

Previous post about my blown LS7:

http://forums.corvetteforum.com/c6-z...30k-miles.html

Dropped the car of at the dealer yesterday to get a "Service Active Handling", "Service Traction Control" and Check engine light diagnosed on my brand new 400 mile replacement LS7.

When I dropped it off, Mark (my service tech that installed the new motor) hooked up the TECH2 device and it showed that I was getting a misfire on #5 cylinder when rpm exceeded 2000 rpm, #8 cylinder was also showing misfire (just not as often). Mark said that misfires can cause the TC and AH to malfunction and he would check it out. BTW, the misfires were imperceptable to me.

Well, he just called. Seem that my 400 mile LS7 has excessive valve guide wear. #5 intake was at .007 when measured using the (apparently GM approved) technique of measuring the valve stem tip movement with the valve spring removed.

Mark said he borrowed a borescope from another tech so he could observe the valve from inside the cylinder as it contacted the valve seat. He observed that the valve was centering as it contacted the valve seat (he was manually moving the valve stem in/out from the top of the head). This means that when the guides have excessive wear, the valves are not contacting the valve seat the way the engineers designed them. I highly doubt hollow stem valves are designed to last 100K miles when they are slamming into the valve guide on off center and then get pushed to the center of the valve seat.

Anyway, new heads (both L & R, less valves, springs, retainers) inbound from Michigan, be here next week.....

Asked Mark (my service tech) to thoroughly check the guides for proper clearance prior to re-assembly as GM's 100% inspection of all LS7s since Feburary 2011 (see sticky - GM response to LS7 valve guide issue summary confirmed) is now highly suspect in my opinion. I'm just glad Mark will have to assemble the heads, so someone I trust will be checking for proper guide clearance. The Wixom suppliers/inspectors probably need a drug test.

Anyway, WTF GM and GO GM cuz it's still under warranty, but Damn.

For everyone else that thinks the LS7 is perfect as delivered, please get out your wallet and get your heads checked. Consider it a one time $450 insurance payment to potentially save you $15,000.

Let the "Sky is falling", "No it's not, my child (Z06) can do no wrong" bickering commence.... can't we all just get along

BTW, love my Z. But that newer younger C7 is looking kinda sexy.

LFZ

WTF....I feel bad for you.

JetBlue427

so much for the 100% inspection test they did on heads after 2011!

'06 Quicksilver Z06

Holy $#!*. You have GOT to be kidding me.

Not trying to "convince" anyone here, but the dough I spent on my heads looks like a better investment with the passing of each day, and I don't even believe that a month has gone by yet, but I can tell you what, after stories like this one and this one, since I have had them done, I have no regrets at this point.

"Go GM" ????? ...... I can see; "Wake up, GM".

gatti-man

This is crazy. How can GM be so lax in their QC?

Les

Just WOW! I'm not even sure what to say at this point. Thanks for putting this out for all of us to see.

TARANTULA

So you paid $450 to get your car diagnosed?

Gary '09 C6

let's all paraphrase together now: "...the problem is only limited to certain 2008--2011 LS7 engines, and has been fixed, and 100% of all suspect engines were inspected..."

Any further questions ?

Dirty Howie

Bill in another thread said it was $850. Did they tell you its only $450 at this dealership?

Looks like you are in good hands and that GM is backing their warranty as they should

sorry for this ..............

GO GM !!!!



DH

JetBlue427

since there built by another company...they would of had to disassemble them to do a QC check after they were recieved. Hopefully that business looses the contract on any further work with GM

gatti-man

GM said they check the guides 100% after feb 2011. Or are we just saying anything GM says at this point is a lie?


I can't tell if you are joking or serious anymore.

CGZO6

Shameless plug for Dirtie Howie

JetBlue427

i was quoted 14 hours plus parts and supplies...so where is this shop that only charges $25 bucks/hr lol

Dirty Howie

I'm serious

You will know when I'm not !!


DH

CGZO6

No, I did not. Motor is a brand new, 400 miles on it, LS7 warranty replacement. See carnage of first engine in link at post #1.

GMuffley

How can this happen in 400 miles?

gatti-man

Then you seriously need to wake up. GM isn't doing right by owners. They essentially gave this guy a time bomb as new. What if he doesn't drive it and it fails out of warranty like others? Or mods it and falls victim to this manufacturing fault and GM doesn't cover it. This isn't right and GM is legally obligated to check every engine. I will start saying go GM when they issue a TSB for all owners and take care of their responsibilities.

'06 Quicksilver Z06

Gary '09 C6

had to be out of spec when delivered to Wixom by the supplier--the heads arrive fully assembled.

Similar issue recently reported in the ZR1 section: "LS9 valve guide wear" thread...

CGZO6

To avoid confusion:
My tech did NOT have to remove the heads to check for excessive valve guide wear. He used the (apparently GM approved) method of removing valve covers and valve springs, then checking how much the valve stem tip will move (radial play - Left/Right, Up/Down as your looking directly at the valve stem tip).

He told the GM advisor that #5 intake had .007 of play.
.002 is the max leaving the factory, .005 is beyond the service limit.

EDIT: He did not use the Super Duper Finger Wiggle method, he used a Micrometer to properly measure the movement.

Tech told advisor that #8 was misfiring as well.
Advisor said replace both heads.

All under warranty.