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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
Thanks! I thought about that as well as many other engine ideas, but I'd rather sell it at this point because I don't have enough spare time to work on it. Someone else could have a fun project! I didn't perform a wiggle test because I thought someone at some point discredited it?
gm did discredit the wiggle test as a indication at their dealers. Mainly because it was done without removing the head and checking from the top of the head. But if you can wiggle the valve in the guide even a little then you were experiencing accelerated guide wear. I’d love to know how good or bad the valves fit in the guides. Possible to check the remaining valves for side to side/ front to back play in the guide?
gm did discredit the wiggle test as a indication at their dealers. Mainly because it was done without removing the head and checking from the top of the head. But if you can wiggle the valve in the guide even a little then you were experiencing accelerated guide wear. I’d love to know how good or bad the valves fit in the guides. Possible to check the remaining valves for side to side/ front to back play in the guide?
To clarify, GM stopped acknowledging a tired and true (20 plus years) procedure becuase they were trying to reduce costs - they pushed this issue back onto the consumer, in that going forward the customer had to pay for expensive labor to remove the heads, pay for the diagnostic to measure and if found "in spec" (air quotes, since GM also increased the out of spec dimensions (sic)) and the heads passed, the customer was on the hook for the bill.
It's all a very transparent attempt to bury the issue, save some cash in warranty work, nothing more. Some say "go GM!"' but in this case it's more like "shame on you, GM!".
Last edited by Dan_the_C5_Man; 01-14-2019 at 03:54 PM.
Sorry for the late response, I've been incredibly busy. I'll try to answer everyone's questions.
The shop returned everything to me, and I looked through all my parts. The lash cap for the broken intake valve is nowhere to be found. I'm guessing it got lost when the issue initially happened. I do think the lash cap was initially there because the heads were replaced a little over two years before, and I put around 6k miles on the new heads. Plus, all the other intake valves had lash caps on them. To answer the question about what my RPMs were when I noticed something was wrong, I think it was somewhere in the mid 3k range.
Here is a pic of the broken rocker arm, which does show some wear from rubbing, but I still believe the lash cap was initially there. Something else must've happened to cause it to come off like others have mentioned: Broken rocker Wear on the broken rocker
In conclusion, I don't think the AHP fix is a bulletproof fix like everyone thinks. And if you look at my post history, I've done nothing but support them and never doubted them once until now. However, I live by facts, and my other intake valves were still showing signs of wear. It doesn't matter if this issue was the rocker arm breaking or something else. It was a matter of what was going to go first. I think reusing the original intake valves is not a good idea. But that's based on my experience. I'm just hoping this info helps fellow members by warning them to still be cautious when they buy new heads. Maybe I'm just one of the few unlucky ones, that could be true as well and everyone else might be ok. Who knows!
I've decided I'm going to sell the car as-is. I have some interested people already. I'm going to still post an ad in the for sale section just in case those fall through.
Again, thanks to everyone for the support, ideas, advice, and everything else. It's been hard on me, but it's now time for me to move on.
The other bearing cup on this rocker looks to be ready to exit it's bore and there is damage around the push rod cup from hammering the end of the push rod. Pad wear as has been noted by another member looks normal. Also in your earlier pictures of the intake valve the damage to the coating up near the keepers is probably from the retainer and using that tool to remove the springs.
It would be useful to some folks given the mileage on these heads to measure the valve guide clearances, but I'm sure you just want to move on.
This issue wasn't fixed all the way with their heads? This means everyone who buys their heads still doesn't have a complete fix? They also "treated" the intake valves (not sure what they did exactly, and when I asked them, they said it's proprietary). I would've bought more at the time had I known I didn't have a complete fix.
In 2011, my '08 Z blew its motor. I had beat the snot out of that C6Z for 36k miles before it went. Tracked it. Road tripped it. Drove it every day to work and back. I gave the car to my stealer under warranty whom I had a great relationship with. I had bought multiple vehicles from them and put the pressure on to find out why my engine failed (I'm also a shade tree mechanic and Software Engineer). Back then nobody knew why there were an alarming amount of engine failures compared to previous Corvettes. I've had 4 late model vettes by that time. All tracked.
The dealer had the GM regional engineer root cause the engine failure and said the problem was from the heads being milled wrong. Had a glorious super-tuner with a brand image of Superman "fixed" the heads with super-expensive exotic parts dipped in holy water, the engine would have still dropped a valve. The valve train geometry was out of alignment because of incorrect head milling and that caused the valves/guides to wear prematurely. I posted the findings here years ago and someone took that information and found a GM engineer to validate the root cause as true.
Were these stock 07 rockers? If so they definitely could have been the root cause. I find it hard to believe it would fall apart otherwise. On another note I’m glad I got brand new intake valves. I can’t believe people reuse stock finicky valves that came out of whopped out stock guides.
every ls7 owners worst nightmare.. very sorry for your loss. you could always put a lq4 with a cam or something back in for cheap and still enjoy the car?
Buy any chance did you check ( wiggle test) if there was any valve guide wear on any of the other intake/exhaust valves? if no other valves are loose in the guides id be willing to blame the rocker as the fail point.
best of luck moving forward!!
This is what I was thinking. For like $1500 you could have your car back and go another 50k with 6L of fun...
check this out, this is a stock 6L engine in a Colorado, all it has is a cam, springs, and turbocharged (and enough fuel of course)
That guy made around 300 dyno passes ranging from 500 to 1000rwhp on a dynojet with that stock internals engine, and raced it for a couple years tuning it into the 9's
I sold the car, so I didn't do a wiggle test. Since we can see the wear (isn't that what it's checking for?), I'm betting the wiggle test would've failed.
Originally Posted by tomcat11
The other bearing cup on this rocker looks to be ready to exit it's bore and there is damage around the push rod cup from hammering the end of the push rod. Pad wear as has been noted by another member looks normal. Also in your earlier pictures of the intake valve the damage to the coating up near the keepers is probably from the retainer and using that tool to remove the springs.
It would be useful to some folks given the mileage on these heads to measure the valve guide clearances, but I'm sure you just want to move on.
The tool did not damage anything when I removed the springs. I took a picture before I touched anything, and the tip of the valve looks exactly the same. Yeah I did just want to move on because I realized I wasn't going to get any warranty on my heads or anything.
Originally Posted by rio95
Were these stock 07 rockers? If so they definitely could have been the root cause. I find it hard to believe it would fall apart otherwise. On another note I’m glad I got brand new intake valves. I can’t believe people reuse stock finicky valves that came out of whopped out stock guides.
Yes, they were stock. I didn't change them.
Originally Posted by Sox-Fan
I know that I am really late to the party, but which trunion upgrade kit was in this?
According to my invoice from AHP, I don't think they changed that. I didn't see it on my invoice. Should they have changed it?
Originally Posted by Frankie2blue
AHP has no opinion on any of this, or did I miss it?
They told me a root cause is hard to identify in this case. After that, I sent an email to them about my other intake valves showing wear. I included a picture of my cylinder #7 intake valve with the cracks to warn them about reusing stock intake valves. I have not heard a response.
They told me a root cause is hard to identify in this case. After that, I sent an email to them about my other intake valves showing wear. I included a picture of my cylinder #7 intake valve with the cracks to warn them about reusing stock intake valves. I have not heard a response.
I find this somewhat disheartening that AHP decided to NOT respond to this thread. I had planned on using them in the future and this may impact on my decision.
According to my invoice from AHP, I don't think they changed that. I didn't see it on my invoice. Should they have changed it?
Oh, I don't know that you needed to. Only reason I asked is that somewhere along the line someone mentioned a CHE Trunion upgrade and yet when I look at the broken rocker I see no C-clips. Thought that was odd, so I asked for clarification in case I had missed something, somewhere. All good.
Oh, I don't know that you needed to. Only reason I asked is that somewhere along the line someone mentioned a CHE Trunion upgrade and yet when I look at the broken rocker I see no C-clips. Thought that was odd, so I asked for clarification in case I had missed something, somewhere. All good.
I think that rocker arm may very well be the instigator, here. It is clear the rocker arm end cap in your picture above let go and all the needle bearings fell out, on top of your trunnion literally snapping in half. There is a well known issue with MY 2007 LS7's attributed to a bad batch of rocker arms from the supplier, in particular the needle bearing trunnions. I believe the dates of those affected are those motors built between 01/2007 through 06/2007, but there were random instances before and after that date.
Look at it from a statistical probability perspective. If AHP did 700 sets of LS7 heads last year alone, there are 8 Ti intake valves per set, so that's 5,600 Ti intake valves that they either re-used or replaced, per their normal process of inspection and tumble polishing. The total number to date is probably in the thousands of sets, on top of all the Ti intake valves from the LS9 heads, as well. All it takes is just one of those Ti valves to fail and grenade a motor, and if there was an issue there with the Ti valves, I'd be surprised if we wouldn't all know about it here in the forum fairly soon after. And AHP is certainly not the only shop who inspects and reuses Ti intake valves, on top of that.
Given that your Z06 is a 2007 on the original rocker arms, in my mind, I really think this was a bum rocker arm likely going back to the known issue of a bad batch of rocker arms that plagued the 2007's when they were new. I know we all may not have been around this forum 10+ years ago, but there is a ton of posts on this if you want to look further into it. We know the 2007 rocker arm issue was/is real, and that just makes the most sense here; the failure started when the end cap on the trunnion came off, the needle bearings flew out, and it was a ripple effect of destruction from there.
Me personally, even on my 2012 LS7, I went with the CHE trunnion kit when I did my heads and cam because in large part, of both CHE and their trunnion kit's stellar reputation. Also, CHE uses the same manganese bronze in their trunnion kit as they do in their valve guides, and you can tell just by looking at it, in my opinion it just looks like a much better design than the needle bearing design. Sure, for the most part, the GM needle bearing rocker arms are probably just fine and GM isn't going to spend the extra coin on CHE's superior trunnions, (if you don't know why, you don't know GM very well,) but, and especially if you have a 2007 LS7, I'd strongly suggest to anybody that they consider the CHE trunnion upgrade. $200 at TSP at the link below for a small piece of mind.
Check out post #708 in the thread below way back from 2011; the head of the intake valve in the picture below that is stuck in the chamber looks awfully familiar.
I find this somewhat disheartening that AHP decided to NOT respond to this thread. I had planned on using them in the future and this may impact on my decision.
I agree that I also disappointed that AHP did not respond to this or even inspect the heads for wear. Sounds like GM's way of dealing with the issue and we see how well that worked out for the customer. I don't know what caused the failure but it appears AHP did not offer any kind of assistance nor seemed to care what failed. This reinforces that concern that the root cause has not been identified. I have a set of used AHP heads I was going to install on a customer's car but now after this I have to inspect/measure the work performed by AHP before installing them. Not very positive for AHP and depending on measurements might be the last set of AHP heads I install.
We took time talking to the OP on the phone about this on several occasions.
We took time and exchanged several detailed back and forth emails with the OP.
We spent a decent amount of time communicating with the OP after his issue occurred (several weeks worth of communications). We repeatedly offered help/assist to the OP in any way we could.
The first time we spoke to OP he was worried that his recent oil system mods may have caused an issue/s and or that some thing was recently done incorrectly by another shop.
We offered to have the OP drop his vehicle off at out shop for inspection (he is in so cal after all). We also offered to inspect the heads, engine etc... OP expressed that he was not in the best financial situation so we even offered to keep the car in our parking lot for a while....
OP Declined All our offers!
I will say the communication between the OP and our shop was not negative in any way and that the OP remained professional throughout his contact with us. I think there were other issues (location issues, storage issues, cost issues, time frame issues, etc...) that lead the OP to decline our offers.
We do 300 plus sets of LS7 heads a year and have done so for 6+ years now! What happened to the OP was unfortunate and undermined as to the cause due to the fact the our offers for inspection were declined. We will not diagnose or guess at pictures or videos over the internet. That is not how any professional conducts failure analysis.
Sorry about the failure...I'm curious who the dealer is...FYI, you can buy a COMPLETE LS7 engine on line for $11k with NO tax and NO shipping...$19k is a real stretch
Greg
Originally Posted by SivaSuryaKshatriya
The dealer is including labor in that price (around ~$8k) which isn't that unreasonable.
Originally Posted by exracer28
I agree that I also disappointed that AHP did not respond to this or even inspect the heads for wear. Sounds like GM's way of dealing with the issue and we see how well that worked out for the customer. I don't know what caused the failure but it appears AHP did not offer any kind of assistance nor seemed to care what failed. This reinforces that concern that the root cause has not been identified. I have a set of used AHP heads I was going to install on a customer's car but now after this I have to inspect/measure the work performed by AHP before installing them. Not very positive for AHP and depending on measurements might be the last set of AHP heads I install.
You did see the part where the OP stated the heads we're redone by AHP "a few years ago" right? It's hard to place blame on anybody after "a few years" especially without knowing the actual point of failure. I suspect the engine was making some noise for at least a short period of time before actually expiring, but at this point it'll be hard to tell what failed first.
We took time talking to the OP on the phone about this on several occasions.
We took time and exchanged several detailed back and forth emails with the OP.
We spent a decent amount of time communicating with the OP after his issue occurred (several weeks worth of communications). We repeatedly offered help/assist to the OP in any way we could.
The first time we spoke to OP he was worried that his recent oil system mods may have caused an issue/s and or that some thing was recently done incorrectly by another shop.
We offered to have the OP drop his vehicle off at out shop for inspection (he is in so cal after all). We also offered to inspect the heads, engine etc... OP expressed that he was not in the best financial situation so we even offered to keep the car in our parking lot for a while....
OP Declined All our offers!
I will say the communication between the OP and our shop was not negative in any way and that the OP remained professional throughout his contact with us. I think there were other issues (location issues, storage issues, cost issues, time frame issues, etc...) that lead the OP to decline our offers.
We do 300 plus sets of LS7 heads a year and have done so for 6+ years now! What happened to the OP was unfortunate and undermined as to the cause due to the fact the our offers for inspection were declined. We will not diagnose or guess at pictures or videos over the internet. That is not how any professional conducts failure analysis.
We have been in contact, like I mentioned in this thread. Even said you were being nice and helpful in post 34! No, I was never worried that an oil mod was the cause. Otherwise I would've called the shop who enlarged my dry sump tank, which I never did because I knew that wasn't the issue. I'm not sure what I said made you think that, but it's not a big deal! Maybe it was me guessing/thinking out loud early on before the engine tear down.
I didn't drop it off because I wanted a faster fix (if I were to fix it) because you guys were totally booked, and I didn't want my car sitting outside for a few months (your shop mentioned the earliest would've been in February sometime, and I was calling in December initially). Yes I'm in Socal, but it is still expensive to tow the car, me being over 100 miles away. Correct, I did not want to dump more money into this car, although I was on the fence to fix it. I was all over the place with what to do about this car, as I've expressed in this thread multiple times.
I also wanted to see if I could get some financial help on the repair from a dealer I have been going to for many years because someone I knew received a goodwill repair before on a blown Z06 (it was years ago though closer to when C6s were still being produced), so that didn't work out. That was another reason bringing it somewhere else.
Anyway, I must admit I'm sad that you are choosing not to even speak about the wear shown in the pictures, especially on my cylinder 7 intake valve. I agree you shouldn't do an actual diagnosis like that, but I feel like those pictures should be taken into consideration when you reuse intake valves in the future. What happened to me is in the past, no one is going to change that, so me bringing this up isn't about me. I just wouldn't want anyone else in the Corvette community to go through what I went through.
You did see the part where the OP stated the heads we're redone by AHP "a few years ago" right? It's hard to place blame on anybody after "a few years" especially without knowing the actual point of failure. I suspect the engine was making some noise for at least a short period of time before actually expiring, but at this point it'll be hard to tell what failed first.
When talking about the heads, it shouldn't matter what failed first. The broken rocker won't cause cylinder 7 intake valve wear (but if it does, please correct me if I'm wrong. I'm being sincere about that, I'm not expert about engine internals). My last remaining points is that shops should reconsider reusing those intake valves.
I didn't hear any unusual noise at all, by the way. The car was super strong still moments before this first started happening, and it sounded great. Maybe I didn't hear anything because of the exhaust, that's perfectly possible.
I’m starting to rethink this on my heads and maybe going the route of Katech and use all their ti valves etc, even though it will be a lot more costly. I have a C7 I drive most of the time and my bone stock Z literally sits under its cover in limbo with 10000 miles on it and I have been waiting and watching these threads to see what happens. I’m not liking what I am seeing in this thread at all and this is after I had already pretty much decided to go the AHP route with MS90 etc.. Either that or just sell the friggin car as is. Once these heads are done I never want to think about this again. My car has been nothing but a babied garage car show queen ( I have never even run it to redline ever) and all this crap has taken every bit of pleasure out of it for me, not to mention I can’t even find anyone I trust in SW Florida to do the R&R on the heads. So now I’m feeling like it’s coming to shipping the car to Katech or just put it up and sell it. And lately I’m getting frustrated enough with this to get rid of it and never look back. I can’t believe we can send men to the moon and back and still have not definitively solved this ridiculous LS7 valve issue. Remarkable, really.
I agree that I also disappointed that AHP did not respond to this or even inspect the heads for wear. Sounds like GM's way of dealing with the issue and we see how well that worked out for the customer. I don't know what caused the failure but it appears AHP did not offer any kind of assistance nor seemed to care what failed. This reinforces that concern that the root cause has not been identified. I have a set of used AHP heads I was going to install on a customer's car but now after this I have to inspect/measure the work performed by AHP before installing them. Not very positive for AHP and depending on measurements might be the last set of AHP heads I install.
Well then since you feel that way please send me the heads and I will take them.
Last edited by Mark Leger; 01-23-2019 at 06:49 PM.
01-14-2019, 03:23 PM
