Tech

You don't have to discount the car. It's not broken. If anything, it's more valuable if it's part of the X% of cars that weren't affected by the problem.

reasonable suspicion

OMG pe0ple are STILL arguing about the guides lol.

actually no one should sell a c6z06, just keep...... but if you do, just tell the truth. Let the buyer worry about it.

JayhawkCPA

^This^

Also, it seems Grand Sports and ZO6's are pretty close in price these days...so maybe the market already accounts for the head issue...who knows...

You can be as stubborn as you want with your price depending on how fast you want to sell it. Good luck with your sale!

grcor

There are several issues with the LS7 heads, not just one. The 2 biggest issues are the firm Chevrolet used to machine the heads did a poor job at machining the valve guide and valve seat concentricity affecting all model years. As the valve opens and closes it rocks back and forth in the guide overstressing the valve stem leading to valve failure (this can happen to both the intake and exhaust valves). In addition the exhaust valves used from the start of production to May 2008 are subject to failure because of their poor quality. The hollow valve stem does not have a consistent wall thickness and the weight of these valves can very as much as 4 grams. After May 2008 Chevrolet started buying exhaust valves from Mahle which have a consistent thickness that is double the thickness of the previous valves. This is why 2006 - 2008 LS7 are more likely to drop exhaust valves.

The next issue is with the titanium intake valves. Titanium engine parts have to have a coating placed on them or they will wear very quickly. The manufacture put a chrome-nitride coating on intake valves, unfortunately this coating can have a rough finish which will wear the valve guide. The manufacture has an addition process that polishes the coating, but Chevrolet did NOT include this polishing process in the specification for the LS7 intake valves. This is why 2009 - 2013 LS7 are more likely to drop intake valves.

You think that your ZR1(LS9) is immune to these issues, well I have news for you. The LS9 has titanium intake valves from the same manufacture and Chevrolet did NOT include the polishing process in the specification for them either. So LS9 owners are going to have accelerated intake valve guide wear.

With the C7 Z06(LT4) Chevrolet finally decided to include the polishing process for the titanium intake valves.

Unreal

Agreed, not only is it an issue with ls7 motors, but ls9 are having same issue.

SilverNotch7

This is interesting, thanks for the information. My own opinion is the redline difference of 6500 vs 7000 rpm for LS9 vs LS7 is making a difference in the failure rate. Is polishing the OEM titanium intake valves something that shops do? I guess if they polish the coating all the way off that would also not be good. I suppose that's why people go with brass valve guides and new valves.

grcor

AHP sends the intake valves back to the manufacture for polishing. Any valve that does not pass inspection does not get reused. WCCH will have the intake valves coated with molybdenum to be compatible with bronze guides if you are willing to pay the extra cost.

Mamo believes that increased valve guide wear is related to not enough oil getting to the guide, so he cuts a small slit into the valve stem seal. AHP has PM guides made to his specification which include a spiral cut in the valve guide to retain oil. This next part I feel is a contributing factor and not a main cause. The 2006 – 2010 Z06s use a large air/oil cooler mounted in front of the radiator which keeps the oil way to cold in normal street driving. Cold oil has a higher viscosity and does not lubricate as well. The 2011 - 2013 Z06's moved to the ZR1 coolant/oil cooler assembly to cool/warm engine oil. Why did they not move to ZR1 coolant/oil cooler assembly back in 2009 which is when the ZR1 came out? Z06 oil pans starting back to late 2007 or early 2008 model year had the predrilled and taped holes to mount coolant/oil cooler assembly.

You will have to ask what other shops do. It would appear that most other shops are not taking this extra step.

Cap'n Pete

The onus is always on the BUYER of a new car. As a seller, you should be open and honest. So IF a potential buyer asks (if they're aware of the issue) then you can be honest and tell them NO, you have done nothing to your engine, and have had no problems to date.

I'd say if a buyer is so inclined, THEY can pay out of THEIR pocket to have the valve covers pulled and perform the wiggle test. Then they (and you) will have an indication. Then you may feel obliged to knock $1400 off the price.

Otherwise, like with any other used car, "buyer beware". It's up to the un/informed buyer to deal with any issues after purchase as they see fit.

As for your engine though, have you noticed any excessive oil usage at all? Before my motor went (in my previous Z) it drank ~2qts in ~2k. Apparently that should have been a sign!

GLWS

BTW: I just recently purchased another C6Z. Paid good money for it. As far as I know, the heads haven't been touched. I've got some money sat aside, and will likely have my heads done in the spring, as I DO plan to A) keep this car a long time, and B) drive the crap out of it (...including tracking it) so I want to have "confidence" in the engine, but I did not ask to have money knocked off the price due to a "potential" issue which was beyond the dealership's knowledge/control.

JerriVette

3/4 s of one percent of all 427 s built that went into camaro z/28s, 427 convertible c6 s and z06 s actually had a mis cast angle of the valve that caused the "stupid" head issue.

The internet has blown this out of portion and every engine failure is incorrectly blamed on the "head" issue.

Just set your price and listen to offers. When one comes along that your accepting of sell your car.

99 percent of all heads that tuner said were defective were incorrectly tested by tuners and the tuners reported the heads needed to be addressed and they made money. As per GM guidelines you can not properly assess the heads with the heads on the vehicle. The "wiggle" test is not an accurate meathod to determine if the heads are defective.

This is ridiculous already...the person doing a wiggle test might as well dance around your car to see if the rain gods bless the vehicle...it's a worthless test.

Knock half the money for the heads and let the buyer do as he pleases as he wastes his money refreshing the heads even though it's not needed.

I'm sorry to hear you having this trouble. My suggestion is sell your car on autotrader and forget about the forum. The vultures are out to find as many things as possible to knock your asking price down.

Find a middle ground and take the best offer or keep the car.

If the roof came off the c6 z06 I'd be driving one.

Awesome sports car. Awesome value.

Good luck.

sublime1996525

Just say no.

TXGS507

Price your car $2K above what you will TAKE for it, not want you WANT for it... Make the potential buyer feel as though he is getting a deal. In the grand scheme of things $2K, $2500 shouldn't keep you from selling.

NotreOkc

I clearly stated not all LS7's had issues. He clearly replied not so. You chose to pull the 70% out of there in your interpretation. He is guessing. Just as you are.

NotreOkc

OMG. Why would anyone even buy a Z06 or a ZR1?? They are going to blow up!! Seriously?
My Z06 never had an issue. My ZR1 has never had an issue. Do you just think the entire sky is falling? Why are you even on this forum is you think C6's are all going to fail?

Tech

You just want to argue. You read his first sentence and glazed over the rest. If only 70% had failures at AHP, then clearly 30% did not. In which case 100% failure rate cannot be accurate. Basic logic from grade school.

NotreOkc

Seriously? Again, you are choosing to take sides and decipher what you wish. I said NOT ALL LS7's had issues. Which is 100% true. He said Not so. What part of not so do you not understand from his response? He went on to say 70% of LS7's that went to ONE shop had guides out of spec. But when I say not all LS7's had issues and he says not so, what part of that are you missing?
Agreed, grade school logic.

Tech

I'm not taking any sides. I don't know either of you. You said more than one thing in your post. So did he. Remove "Not so!!" from his post and then read his post. The entirety of a comment matters, not just the first sentence.

Unreal

People saying it isn't a big issue are delusional and living in their own happy magic place with their head buried in the sand. Out of 30+ heads I've seen inspected, one was in spec, and just barely. All the others have been grossly out. While the wiggle test may not be 100% accurate to get specific numbers, it is more than adequate to show gross slop. Saying wiggle test doesn't work would be like saying you need calipers to measure if a fish is longer than 2", and sitting there with a 26" salmon in front of you saying "geez, I don't know, better get the calipers to measure to see if it is over 2".

No need to argue what the OP should do. He just needs to be honest. As for what he will take, how to sell a car, etc, that is all on him. If he doesn't like the offers he gets, then he won't sell it, or he will lower the price. It reassuring to see that the message is getting out, and that new owners are protecting themselves from a huge mistake.

grcor

Your one of those people who say the everyone else is paranoid, but you are the one who sold your car! I still own mine and yes, I did get my heads fixed. Now I can drive my car and not worried about it. But unfortunately, you now have to think about your intake valve guide wearing away as you drive. I seriously hope you did not hear BOOM! It will be very expensive.

Unreal

Why would anyone buy one? Because the fix is quick, simple, easy and cost as much as a set of tires. So why not? It is an easy to fix issue. Its like not buying a z06 or zr1 because a brake job cost a lot, or tires are $1500. It isn't a unfixable or stupid expensive thing. Buy a car, check to see if it has an issue (free to $200) and then fix it if needed ($800-2000) and be done.

NotreOkc

He said Not so! So I cannot remove it. My only point. I know this issue has been beat to death.