LS7 Failures in the Z/28's How Many?

[JeffInDFW]

Originally Posted by DasBaldDog

Correct me if I'm wrong, but didn't Hib also say in updates to that article and other postings that they received NEW LS7 heads from Chevy made as late as 2016 that have valve guides out of spec?


Found it, see page 24. https://www.corvetteactioncenter.com...-engine24.html

I believe I've read other commentary by Hib expositing on the new heads and others he has seen that were similarly offensive.

You are exactly correct. Hib wrote that amazing article on the LS7 and has stayed up to date with it as he owned a C6 Z06 (he still does). His heads were found out of spec by the GM dealer, and in 2016 new heads were ordered for the car by the dealership. Every intake valve on the new replacement heads were out of spec and half of them were WORSE than the bad heads that were being removed/replaced on his car. So much for total inspection.

I remember threads on CF where the guys were able to figure out that they think there were two machines at the head manufacturer that were machining the original heads, and one of the machines was set up out of spec. I can't find that thread, and its been too long now to remember how they came to that conclusion.

The percentage of failures cited by GM is absolute total BS. Period. The guys on CF tracked the number of reported failures, again you can search for the threads there. "100% inspection starting in 2011" has been proven to be a total lie too as cars after 2011 also had heads wildly out of spec and failing. Go search CF.

Katech got involved and sent info to GM showing what they had learned about the cause of the dropped valves. Soon after that was sent to GM (GM sent reps to Katech to talk to them), GM went totally silent and then the lawsuit was filed (which was rejected). Read all about it on CF.

BUT......I have been watching you guys here, and I'm not seeing that widespread issue with the Z/28's LS7. I would give anything for someone inside GM to leak the real details of this debacle and let us know if by the time the 2014 Z/28 was being built did they finally get control of this issue? I feel we would be seeing a lot of those problems here by now, and it seems like we aren't. I hope so, because the LS7 is my favorite engine of all time. Its why I've followed this so closely since it first began to be taken seriously around 2008. But like the poster above, I would love to see you guys work together like the Z06 guys did on CF and track info together for each other.

Best of luck guys. I hope to add a Z/28 to my stable someday.

[hjdca]

Regarding postings here on the forum, we have not seen even one Z/28 head with the valve guides out of spec.. So, it seems the issue was fixed with the vette run as articulated by GM.

[JeffInDFW]

https://www.camaro5.com/forums/showt...1#post10497269

2013blackgt posted:
I had Katech install their stage 2 LS7 package on my z/28 and they said my valve guides were out of spec. I don't have the numbers though, they never gave them to me. Fyi, my car had 7,800 miles on it when they did the work.

[The_Raging_Bull]

Originally Posted by DasBaldDog

Correct me if I'm wrong, but didn't Hib also say in updates to that article and other postings that they received NEW LS7 heads from Chevy made as late as 2016 that have valve guides out of spec?


Found it, see page 24. https://www.corvetteactioncenter.com...-engine24.html

I believe I've read other commentary by Hib expositing on the new heads and others he has seen that were similarly offensive.

sorry for the later post, yes on checking your post is spot on. However as I said my fix on my 09 LS7 was stud mounted roller rockers, as it prevents side loading forces and the valve drop issue.


I hadn't seen that the lawsuit was rejected, I'll catch up with that on CF, but this subject over there has been a source of rampant speculation where people with nothing to add comment just to run yup their post totals.

[DasBaldDog]

Originally Posted by The_Raging_Bull

sorry for the later post, yes on checking your post is spot on. However as I said my fix on my 09 LS7 was stud mounted roller rockers, as it prevents side loading forces and the valve drop issue.


I hadn't seen that the lawsuit was rejected, I'll catch up with that on CF, but this subject over there has been a source of rampant speculation where people with nothing to add comment just to run yup their post totals.

What I find interesting is that everyone is assuming that the valve guides are wearing when the only evidence I have seen shows that valve guides are out of spec, not that they are necessarily worn.

So they test valve guides that are 0.012 and say they they are worn out, but Hib's measurements showed that some are coming in brand new around there. So the valve guides might not be wearing at all or very little, they are so out of spec as to appear worn when brand new. Meanwhile Katech and others are installing softer guides that are running (one or two instances) 30,000+ miles with "no wear". If the sideloading and whatnot will murder PM guides in 3,000 miles, I do not understand bronze guides going 30k with no appreciable wear.


Just a thought.



While I have your attention though, do you have a build thread, or what can you tell me about your roller rockers. I have been planning on doing a Head/Cam/Headers package on my Z and have been kicking around the roller rocker idea (I've never owned a V8 where I DIDN'T install rollers... but man LS7 stuff is pricey)

[Katech_Zach]

Nearly all LS7 heads are prone to the valve guide issue. We believe we have the best solution to solving this using our Katech Ti/Mo valves and bronze valve guides.

Here is an article my coworker Jason wrote on the corvetteforum showing an update on a vehicle with our solution. https://www.corvetteforum.com/forums...rack-days.html

The vehicle had approximately 21,000 miles out on his car after the solution with nearly 10 hours of HPDE.

[cmancha003]

I just got confirmation that one of mine is bad. At the dealership right now. Hopefully the previous owner didn't tune the car. 33000 miles on it. Will know more this week I think.

[j o n]

Originally Posted by cmancha003

I just got confirmation that one of mine is bad. At the dealership right now. Hopefully the previous owner didn't tune the car. 33000 miles on it. Will know more this week I think.

How'd you end up at the dealership with it? Noise? Quit running? Check engine light?

[cmancha003]

Noise. It wasn't terribly loud (had a Subaru in the past so about a loud as their lifter tick) but I, like some of you, have heard the stories and decided why not ask the dealership while i was there for an oil change. No check engine light, no shacking or anything. Power seemed fine or at least close enough. Are they just doing it for the warranty work? I haven't seen anything yet as I just took it in this morning. I will try to keep everyone updated.

[X77-69z28]

Please do! I’m losing sleep over this!

[Katech_Zach]

Originally Posted by cmancha003

Noise. It wasn't terribly loud (had a Subaru in the past so about a loud as their lifter tick) but I, like some of you, have heard the stories and decided why not ask the dealership while i was there for an oil change. No check engine light, no shacking or anything. Power seemed fine or at least close enough. Are they just doing it for the warranty work? I haven't seen anything yet as I just took it in this morning. I will try to keep everyone updated.

Unfortunately, most dealerships will not address this as warranty work. I have experienced this first hand with a C6 Z06 that was in my family's possession.

If they give you a hassle, Katech would love to help you out.

[69L48Z27]

Originally Posted by cmancha003

I just got confirmation that one of mine is bad. At the dealership right now. Hopefully the previous owner didn't tune the car. 33000 miles on it. Will know more this week I think.

You confirmed that one of what is bad? Thread is for LS7 failures, doesn’t sound like you have a grenaded engine.

[1970judge]

Originally Posted by 69L48Z27

You confirmed that one of what is bad? Thread is for LS7 failures, doesn’t sound like you have a grenaded engine.

Kind of what I am wondering? 'What' is bad?

[BJJKRIS]

So I’m about to send my heads off as a core return to AHP. I’ll ask them to give me the specs on how far they’re out of tolerance if at all. Be interesting to see for sure.


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