[Z06] Oh shit value guide issue?!
#1
Drifting
Thread Starter
Oh **** value guide issue?!
Very aware of all the questions about the value guide issue with the LS7.
I have 23,000 trouble free miles on a stock 2011 LS7. Very little valve noise at about 1,700 rpm. Been like that since the day I brought it home brand new.
Started the car today and notice a loud ticking noise and when i started to accelerate, there was a slight surge. and stumble.Turned the car around and right back into garage. Does this seem like the dreaded value guide issue? Would driving it cause a rod through the block?
I have 23,000 trouble free miles on a stock 2011 LS7. Very little valve noise at about 1,700 rpm. Been like that since the day I brought it home brand new.
Started the car today and notice a loud ticking noise and when i started to accelerate, there was a slight surge. and stumble.Turned the car around and right back into garage. Does this seem like the dreaded value guide issue? Would driving it cause a rod through the block?
Last edited by Crossofiron; 11-11-2018 at 01:35 PM.
#2
Melting Slicks
Very aware of all the questions about the value guide issue with the LS7.
I have 23,000 trouble free miles on a stock 2011 LS7. Very little valve noise at about 1,700 rpm. Been like that since the day I brought it home brand new.
Started the car today and notice a loud ticking noise and when i started to accelerate, there was a slight surge. and stumble.Turned the car around and right back into garage. Does this seem like the dreaded valy guide issue? Would driving it cause a rod through the block?
I have 23,000 trouble free miles on a stock 2011 LS7. Very little valve noise at about 1,700 rpm. Been like that since the day I brought it home brand new.
Started the car today and notice a loud ticking noise and when i started to accelerate, there was a slight surge. and stumble.Turned the car around and right back into garage. Does this seem like the dreaded valy guide issue? Would driving it cause a rod through the block?
Good luck!
#5
Le Mans Master
It could be anything .. Spark plug wire popped off, broken valve spring, etc.
But I'm confused - you say "..well aware of the valve guide issues..", but you didn't mention, at 20K plus miles, that you've pulled a valve cover to check anything.
Learn from this guy.. https://www.corvetteforum.com/forums...alve-list.html
Don't be a statistic. Pretending "that stuff happens to other people" won't get you very far.
But I'm confused - you say "..well aware of the valve guide issues..", but you didn't mention, at 20K plus miles, that you've pulled a valve cover to check anything.
Learn from this guy.. https://www.corvetteforum.com/forums...alve-list.html
Don't be a statistic. Pretending "that stuff happens to other people" won't get you very far.
Last edited by Dan_the_C5_Man; 11-10-2018 at 11:37 PM.
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Landru (11-11-2018)
#6
I heard a similar loud ticking, like the sewing machine noise only amplified. Luckily I was on base and going less than 5 mph and shut it down within 400m. Ended up have a few broke valve springs and my AHP heads were a few weeks from being delivered. It could be a few things from a loose or bad plug to a failed lifter or broken valve springs. Definitely don’t drive it, pull the covers and check it out. Looks like you caught it before it committed LS7 suicide but that doesn’t mean it’s an easy fix. I “only” had broken valve springs but it still ended up costing a good bit of money to make it right. I could have went a cheaper route but figured while the block is out I mine as well make everything right and upgrade and replace everything in the block. Good luck man, I hope it’s a simple fix for you. Only advice I have is find a good reliable shop, keep the machine shop and mechanic separate and trust no one. Lots of shady JV shops out there, seems like the good ones are getting harder and harder to find.
#7
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2020 C5 of the Year Finalist - Unmodified
Very aware of all the questions about the value guide issue with the LS7.
I have 23,000 trouble free miles on a stock 2011 LS7. Very little valve noise at about 1,700 rpm. Been like that since the day I brought it home brand new.
Started the car today and notice a loud ticking noise and when i started to accelerate, there was a slight surge. and stumble.Turned the car around and right back into garage. Does this seem like the dreaded valy guide issue? Would driving it cause a rod through the block?
I have 23,000 trouble free miles on a stock 2011 LS7. Very little valve noise at about 1,700 rpm. Been like that since the day I brought it home brand new.
Started the car today and notice a loud ticking noise and when i started to accelerate, there was a slight surge. and stumble.Turned the car around and right back into garage. Does this seem like the dreaded valy guide issue? Would driving it cause a rod through the block?
#8
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St. Jude Donor '05
If its loud and stumbling you could already have had a failure I wouldnt even start it. You can pull plugs and stick a borescope in ea cyl if youre curious..
The whole head issue...what a black eye for GM.
The whole head issue...what a black eye for GM.
Last edited by cv67; 11-11-2018 at 10:07 AM.
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Landru (11-11-2018)
#10
Race Director
It could also be a cam lobe starting to go. That's not exactly uncommon. I've had that happen in addition to two head replacements due to excessive valve guide wear. If you find guide wear and have the heads gone through, be sure to have the cam looked over while things are opened up. Good luck.
#11
Race Director
No excuse, really.
LS7 owners have an obligation to inform themselves w/ this motor.
IF they don't when this well known issue occurs it's on them, sorry to say.
Can't un-ring the bell, now.
I have 23,000 trouble free miles on a stock 2011 LS7. Very little valve noise at about 1,700 rpm. Been like that since the day I brought it home brand new...Started the car today and notice a loud ticking noise and when i started to accelerate, there was a slight surge. and stumble.Turned the car around and right back into garage. Does this seem like the dreaded valy guide issue? Would driving it cause a rod through the block?
It'd have seized-up right then & there w/ oil/coolant everywhere underneath via hole in block.
Do NOT attempt starting & get it inspected post haste, might've got lucky if only a spring etc.
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Crossofiron (11-11-2018)
#12
Drifting
Thread Starter
Going to have it flatbeded to Heritage tomorrow
Thanks for all the advice. I had hoped that I would not get screwed from a discussion with the Bowling Green Plant Manager at a Corvette Corral function at a ALMS race at Laguna Seca about 5 years ago where he told me that the "bad heads" did not affect the 2011 year. Same thing that I heard from a variety of other so called experts. from the dealership to some folks here on the Forum.
I will know what the real issue is after I get it torn down by American Heritage. Lucky for me they are only 45 miles away!
I will know what the real issue is after I get it torn down by American Heritage. Lucky for me they are only 45 miles away!
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Landru (11-12-2018)
#13
Instructor
I have a 2011 and about 27,000 miles just in the process of doing the heads there where a bunch of guides out of spec. Cam was also just starting to go so new cam as well. Sent my intake valves back to Del West to have them super finished which is a no charge item by the way all where good so did not need to buy any new intakes. Replaced exhausts with Ferrera hollow stem exhausts. Cam is crap surface hardening just starting to go and its not straight so have replaced that with a Cam Motion with there highest quality core material, also from what I have seen in mine the cam goes first then takes out the lifters then you lose the motor some feel the lifters go first but its hard to diagnose an engine post mortem that has had major destruction, in my case I was lucky to be able to witness first hand the cam was going first most lifters where still good but have replaced them with much better Johnson slow leak down ones. Also the cam chain had so much stretch in it check yours carefully. Should have the heads back from the machine shop next week so I can finish reassembly. Highly recommend you put in better pushrods the stock GM ones are junk I have some that are .032 out of column, also do some kind of rocker bearing upgrade.
Last edited by G8Pumpkin; 11-11-2018 at 03:07 PM.
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Crossofiron (11-11-2018)
#14
I'm going to be pulling the heads soon and my 39k mile Z06, whats the best way to check the cam? Pull the lifters and look for scoring?
Last edited by OneMeanZ; 11-11-2018 at 10:54 PM.
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Thanks for all the advice. I had hoped that I would not get screwed from a discussion with the Bowling Green Plant Manager at a Corvette Corral function at a ALMS race at Laguna Seca about 5 years ago where he told me that the "bad heads" did not affect the 2011 year. Same thing that I heard from a variety of other so called experts. from the dealership to some folks here on the Forum.
I will know what the real issue is after I get it torn down by American Heritage. Lucky for me they are only 45 miles away!
I will know what the real issue is after I get it torn down by American Heritage. Lucky for me they are only 45 miles away!
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Landru (11-12-2018)
#16
Instructor
Yes just take out the lifters and look at the cam carefully if there is any sign of the case hardening starting to wear replace the cam. At this point also change the timing chain I used the c5r race chain if I had to do it again would look into a Cloyes double roller but do not know if there are clearance issues somebody will know what fits that is better than stock as it is obviously not good enough judging by the slop in mine so there was no hope of it giving accurate cam timing. The cam can be removed without taking the engine out but it still is a lot of work. Search ytube for videos, the steering rack does not have to be completely removed from the car, slide it over to the passenger side far enough to get clearance. Also if you are this far into it I replace the crank damper with a middle of the road Power Bond unit or you can go all out for an ATI one, when I inspected mine carefully on the back side the rubber was starting to crack the old damper still ran true but when you have put this much effort into getting this far another few hundred is well spent as I wouldnt want to tear it apart again. I spent a lot of time with an air hose cleaning from the back side the air conditioning condenser as there was lots of crap in it which also impedes air flow to the rad as it sits in front of the rad.
Last edited by G8Pumpkin; 11-12-2018 at 09:13 AM.
#17
Pro
You guys stop the car and send it to the shop for making a sewing machine sound? If I did that, my car would have the same 180 miles on it that it came with. My car has never had a quiet valve train.
Off topic, can I get a refresher on the mechanics of dropped valve? If it slips off the rocker, shouldn't the spring keep it out of the cylinder permanently? The valve enters the head against its will, right?
Thanks
Off topic, can I get a refresher on the mechanics of dropped valve? If it slips off the rocker, shouldn't the spring keep it out of the cylinder permanently? The valve enters the head against its will, right?
Thanks
#18
Drifting
It could also be a cam lobe starting to go. That's not exactly uncommon. I've had that happen in addition to two head replacements due to excessive valve guide wear. If you find guide wear and have the heads gone through, be sure to have the cam looked over while things are opened up. Good luck.
I have a 2011 and about 27,000 miles just in the process of doing the heads there where a bunch of guides out of spec. Cam was also just starting to go so new cam as well. Sent my intake valves back to Del West to have them super finished which is a no charge item by the way all where good so did not need to buy any new intakes. Replaced exhausts with Ferrera hollow stem exhausts. Cam is crap surface hardening just starting to go and its not straight so have replaced that with a Cam Motion with there highest quality core material, also from what I have seen in mine the cam goes first then takes out the lifters then you lose the motor some feel the lifters go first but its hard to diagnose an engine post mortem that has had major destruction, in my case I was lucky to be able to witness first hand the cam was going first most lifters where still good but have replaced them with much better Johnson slow leak down ones. Also the cam chain had so much stretch in it check yours carefully. Should have the heads back from the machine shop next week so I can finish reassembly. Highly recommend you put in better pushrods the stock GM ones are junk I have some that are .032 out of column, also do some kind of rocker bearing upgrade.
Yes just take out the lifters and look at the cam carefully if there is any sign of the case hardening starting to wear replace the cam. At this point also change the timing chain I used the c5r race chain if I had to do it again would look into a Cloyes double roller but do not know if there are clearance issues somebody will know what fits that is better than stock as it is obviously not good enough judging by the slop in mine so there was no hope of it giving accurate cam timing. The cam can be removed without taking the engine out but it still is a lot of work. Search ytube for videos, the steering rack does not have to be completely removed from the car, slide it over to the passenger side far enough to get clearance. Also if you are this far into it I replace the crank damper with a middle of the road Power Bond unit or you can go all out for an ATI one, when I inspected mine carefully on the back side the rubber was starting to crack the old damper still ran true but when you have put this much effort into getting this far another few hundred is well spent as I wouldnt want to tear it apart again. I spent a lot of time with an air hose cleaning from the back side the air conditioning condenser as there was lots of crap in it which also impedes air flow to the rad as it sits in front of the rad.
I agree on the balancer. As long as you already have it out, given the bad reputation for bad balancers in LS motors, I couldn't in good conscience put the OE one back on. The PowerBond Race Series balancer for the LS7 I would argue has a better reputation for durability than the ATI LS7 variant; there has been too many ATI LS7 failures on this forum. I'm sure ATI has whatever was wrong corrected by now, but I wouldn't spend more for the ATI balancer when the PB Race Series LS7 balancer (PB1503SS) is less expensive and a very high-quality part. (And it doesn't have to be re-built over time, which on a Corvette is a big deal given it's not easy swapping the balancer on these cars.)
#19
Drifting
Thread Starter
Different sound this time
Value train always had a bit of clatter at 1700 rpms. That is normal. This time the sound was very different and and the car stumbled leaving driveway. Also way different. Something is wrong and rather than throw a rod and have to spend $14,000, worth it to me to have it towed to American Heritage.
Stay tuned as I will post the findings. Damn.
Stay tuned as I will post the findings. Damn.
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Landru (11-12-2018)
#20
Drifting
You guys stop the car and send it to the shop for making a sewing machine sound? If I did that, my car would have the same 180 miles on it that it came with. My car has never had a quiet valve train.
Off topic, can I get a refresher on the mechanics of dropped valve? If it slips off the rocker, shouldn't the spring keep it out of the cylinder permanently? The valve enters the head against its will, right?
Thanks
Off topic, can I get a refresher on the mechanics of dropped valve? If it slips off the rocker, shouldn't the spring keep it out of the cylinder permanently? The valve enters the head against its will, right?
Thanks