rockinSeat

Summary: If my heads are replaced under warranty, are the new stock parts going to solve the problem? Background info: I bought an 07 stock Z06 at 14k miles and was told car was not tracked or raced. From the condition, I believed the owner and since it came with a GMPP through 2014, I figured it was a good deal. The car is up to 22k now, mainly long highway trips and a few rides to work, still stock; not burning any oil or displaying much for symptoms. Sometimes I thought the car made a funny "spattering" sound, it sounded like the noise was the exhaust, but it came from the front of the car.
After reading the forum, I decided I wanted to get my guides inspected for peace-of-mind. The first dealer I contacted had no clue how to test for guide wear; the second said that it would be a waste of my money and they had never heard of that issue. The third dealer said they had done the test before and would be happy to help.
I didn't know what to expect; I had mixed results from doing the wipe pattern test - looked ok, but a quick wiggle test by hand didn't feel good. I figured being stock with low miles I was wasting my time as the 2nd dealer said. Later in the afternoon, I got a message from the service advisor. He said I had exhaust valve guides that were way out of spec on both sides. He ordered new heads, valves, and springs. I was told the car would be kept inside as the new heads take 2 weeks to arrive from Lancing, Michigan. Once the heads arrived, they would be sent to the machine shop to have the valves seated. I asked about having the rockers replaced, but I was told they were fine.
Over the next couple of weeks, I asked my advisor lots of questions - mainly about whether my car will have this problem again. He told me, if he had to guess, he thought the original guide material in my car was bad. He also did some research and told me that the cylinder heads have a new part number (it is not the 6 digit casting number on the side which remains the same) and that the heads have been redesigned and/or come from a new distributor. He said the exhaust valves are now coated with chromium nitrate. After looking at the newly assembled heads, he also told me that the new guides appeared bronze in color, but were not pure bronze as a test found that a magnet stuck on.
So my car is done now and still being stored inside at the dealer as a couple of blizzards have come by and I can't drive it home yet. Further, they said it got dusty so they are going to detail it inside and out for me. So after all my service advisor has told me, sometimes I think we are a bit in the dark about this issue. For instance:
1) Is the difference with the new valves the chromium nitrate coating and what year did they start using these?

2) Have the cylinder heads changed? Redesign and/or change in supplier? When did this happen?

3) Has the guide material changed or have the guides been coated? Why would they appear bronze? Do magnets stick to bronze guides (i.e. are bronze guides pure bronze all the way through?)

4) Should I be concerned about the rockers? I mean, haven't they been redesigned and if so, wouldn't they be required for the new heads?

5) Is my car fixed now?

One last thing, I strongly recommend all 06 - 07 owners get their guides checked. My car was bone stock and driven by "waxers" - exhaust valve guides were shot. If anyone is in Colorado, I highly recommend Al Serra North of Colorado Springs.

'06 Quicksilver Z06

He may have been talking about the factory intake valves when he mentioned the chromium nitride coating.

http://www.speedtalk.com/forum/viewt...hp?f=1&t=29538

But this has been on the intake valves for years, so really nothing new there.

As far as "new distributor", well, somebody had said that some of these heads had come from out of China. But I always thought they were joking when they said it.

http://forums.corvetteforum.com/c6-z...post1583068293

http://forums.corvetteforum.com/c6-z...post1583214956

biggfroggy

was yours like a sputtering / surging sound and feel? i have a 2006 with 14,000 miles. never raced. the service engine soon light comes on often. when it does you can def tell a difference in how the car drives. it will sputter and surge, especially at higher rpm's. you can hear it through the exhaust as well.

i havent been driving it. im saving to have a lot of work done all at once. instead of cracking open the engine to check the valves, and putting it back together, and then taking it apart to do a cam swap later.

im like you. just because GM swapped the heads, does that really mean its fixed? or did they put the same type of scrap metal back in?

ive been pissed about all of this, and have looked at GT500's, Vipers, and even some Porsches. I just basically have the thing paid off, and as they say when it comes to women "its cheaper to keep her"

rockinSeat

But are the exhaust valves now coated - I think we do know of a part number change and change in mass - is it due to the coating?

'06 Quicksilver Z06

Sounds like a legitimate concern in light of what the forum member below had to say after he did a little more investigation.


In light of the above, are you sure that they put new valves in it, rocking seat?

At any rate, with regard to the part number change, Mark200X did some testing on the old valves vs the new ones, and the only difference he reported was an increase in the wall thickness of the new valves vs the old valves, of about .009".

He discovered this .009" thickness increase, by actually cutting into examples of the sodium "filled" stock valves

He didn't say anything about any new coating on the new exhaust valve he inspected.

If you are wondering what .009" works out to in "practical" terms, well, that works out to the width of about two hairs.


So aside from a slight weight difference, possibly partly due to the two hair width, thickness increase, of the OEM valve hollow metal stem, not much difference did he report in the old valves vs the new.

http://forums.corvetteforum.com/c6-z...issection.html

rockinSeat

When I spoke to a machine shop that had done a few ls7 heads, they told me it's quite common for GM to come out with fixes for cylinder heads and valve train parts - such as with the Cadillacs that were having problems. I can't help but think with changes to the valves and rockers that there have been other changes we don't know about. That's why I'm asking that we press for more info. And you are right, it's cheaper to keep her. I can't afford a zr1 or a gtr, and i have been forever desensitized to be able to enjoy a c6 grandsport.

rockinSeat

I will try and get a parts number list, the test results, and everything I can when I pick up the car. I was told everything would be new except for the rockers, and I double-checked about the valves. The advisor agreed they would have to be replaced since they could have been damaged from the warn guides. It is clear to me that some dealers know more about this than others. I am led to believe that my 07 car now has '13 heads and I was hoping GM has done something to address this problem. It would be a lot more convenient for me.

'06 Quicksilver Z06

I'd still be concerned as to if they replaced all of the valves, or just the valves which came from out of the guides which were worn.

At any rate, good luck with it, and hope you are back on the road up and running soon. :thumbs

rockinSeat

I think I'm even getting new intake valves - we'll see. I had some thoughts out running today - the guy at the dealer was so nice, I wonder if I should have asked if I could have had them put it together with bronze guides. (He did tell me that the heads are not assembled - however, all the parts are gm replacement - the machine shop didn't decide what went in.) The car is back together now, so no point struggling with that one. I also wonder if I should be putting roller rockers on instead. I mean, are the 2012 and 2013 owners concerned about this for the long run? Is GM concerned if they put it in the camaro next year?

spicytuna

I strongly doubt that your they'd install anything other than the OEM guides in your replacement heads. After all, this is a dealer and not a performance shop.

As for the rockers, some 2007 models had an issue with the needle bearings but I'd hope that your dealer would be inspecting the rockers as they re-install them in your heads.

If you want cheap insurance, you could go with the trunnion upgrade kit offered by companies like Comp Camps :
http://forums.corvetteforum.com/c6-p...ial-price.html

But again, I doubt that your dealer would accommodate that during their rebuild of the heads.

JwT

It seems odd to me that GM would not send an assembled set of heads for this replacement. I mean how many dealerships have a machine shop. Not any that I know of, it's strickly remove and replace parts from boxes in the parts department. Anyway you do have new heads and valves. If I were in your shoes I'd have the test done again in 5k miles. Just for piece of mind.

erick_e

I think the cost of the solid titanium intake valves is the primary consideration for GM not using complete head assemblies.

Mark2009

Since no one is able (or willing) to state the exact nature of the problem with original guides, your question cannot be answered. Regardless of what parts are used.

1. The exhaust valves are not CrN coated.
2. Unlikely. Vendors are not showing a part number change. A supplier change, with no change in spec, would normally not be public (published) info.
3. Unlikely. They wouldn't appear bronze. Magnets do not stick to bronze guides in this type of application. Bronze itself is an alloy (not 'pure'), and does not normally contain any significant amount of iron (which would be required to make it magnetic).
4. No, not really*, and no -- unless you're within the 2007 window in the sticky.
5. Nobody knows. Hard truth. But if the machine shop did quality work then your odds are good. Check your guides again in 10K miles or so. Sooner, of course, if you notice anything unusual (noise, performance, etc).


________________________________________ ___________
* a minor change appears to have been made which may affect rigitidity. See http://forums.corvetteforum.com/1582...-post1701.html and http://forums.corvetteforum.com/c6-z...post1582722473

WhiteDiamond

The bolded part leads me to believe you are not getting new valves and valve train related parts. New heads with new guides and your old valves and valve train are probably going in.

GM will not install anything other than the sintered guide in the heads. GM still specs the sintered guide for the LS7.

Since you have new heads/guides, you could consider roller tip'd rockers to prevent any side loading of the valve stem on the guide. You could also look at having them pulled, again, by a vendor and rebuilt with bronze guides.

Mark2009

Look, in the OP he stated that the dealer's service adviser told him that he -- the service adviser -- "ordered new heads, valves, and springs".

So, let's try to keep up with the program in these threads, okay? I don't want to be harsh, but the misinformation in these valve threads long ago reached epic proportions and everyone should really try to be careful, correct, and complete when restating something posted by another.

rockinSeat

Would it be wise to push the issue? I mean, sometimes I feel like asking the manager to ask the regional engineer, etc, is this problem fixed? Another mini-blizzard today, so i won't be able to get the car back, nor discuss. The guides looked so much like bronze that the advisor initially thought they were bronze until I asked him to double check, then he used the magnet to verify attraction. Do the original "sintered" guides appear bronze? I really wonder sometimes why I put up with this super expensive toy when we have to put up with this crap.

'06 Quicksilver Z06

Couple of things rockinSeat.

1. Have you actually seen these heads yourself? Did the guides look like bronze to you?

No, the stock guides do not have a bronze color to them.

The following are photos of one of my WCCH heads with a bronze valve guide in it.





This next photographs, are of one of the same pair of cylinder heads before it was worked by WCCH, but with the stock powdered steel valve guide in it. Intake and exhaust.





2. If you want more solid assurance that this is in fact a new set of heads, with all new parts in them save for the rockers, that you are getting, well then you might be wise to take it up a notch or two beyond what the mechanic is telling you, and "push" the issue, if you are planning on keeping the car for any length of time.

The last thing you want to have happen, is the car fail shortly after going out of warranty.

rockinSeat

I got my car back today! Brand new heads, springs, and all new valves, both intake and exhaust. Again I spoke with the advisor and I was told the heads have a new part number. He said the part number is not shown in the online catalogs and that he had to call Part tech(?) to get the new part numbers. Unfortunately, the computer printout I was given has the same part numbers that Quick looked up for me. I wish someone with the inside scoop could step in here. After all, it was stated above that the stock guides don't look bronze.
I got to see my old heads at the dealer. It was obvious nothing from my old heads was reused. There is a slim chance I could buy my old heads back for a core charge off $300. I thought that might be a good deal - what do you guys think? I thought I could have them rebuilt without having my car out of commission.
Finally, if anyone else out there is thinkiing about going to the dealer for a repair under warranty, there is a slim chance that if the dealer will replace your heads that they would put it back together with bronze guides and SS valves, if you insisted, and you pay for the parts, and you are willing to void your warranty. I didn't even ask about it, but my advisor said it may have been a possibility.
Overall, I'm downright pleased with how I was treated and the service that I got. The car seems to be running smoother and slightly quieter. So please let me know what you think.

1.) I believe the part numbers for the cylinderheads may have changed and we are not aware
2.) would it be worth buying my old heads back if i can?
3.) dealer might be willing to re-assemble your car with bronze/ss if you ask and are willing to pay a few $$ and void your warranty

jedblanks

I think the re cut of the seats is the key. You now have a seat cut to the valve guide and everything is all lined up correctly. Something probably wasn't originally.

'06 Quicksilver Z06

To your part in bold, how does one know this for certain?

You might contact someone like RichieRichZ06 for clarification on whether or not this is true, but it seems unlikely.

If you are talking about the bare castings, depends, but probably not, unless you were planning on using your current intake valves in them.

A new stock titanium intake valve, retails for $127.01. You'll of course need 8. You can get them at GMParts Direct for $75.30 plus their ridiculous pricing on the shipping. I calculated 8 of them there, and it came to $744.41 shipped.

So at $300.00 for your old heads, by the time you pay for a new set of stock intake valves for them, you are going to be at $1044.41, or right where you would be if you were to buy a used set of heads for about $1200.00, and then sold the stock exhaust valves from out of them to somebody looking to buy a set of used stock LS7 exhaust valves.

Of course you would have "new" intake valves, but they would need to be tumble polished anyway for use with bronze guides.

Interesting point, but further review of it brings up another point.

If you had your heads done with bronze guides and SS valves elsewhere, but kept the car on the stock tune and told them nothing of the head work, then they wouldn't touch your warranty, including the transmission, differential, and a number of other things, unless and until they removed your valve covers.

As long as they didn't remove your valves covers, the rest of your warranty, including the rest of the power train, would possibly be OK, because they would have no idea, unless they became suspicious of the additional valve train noise you'll sometimes get with SS valve and dual springs setups and then did decide to remove the valve covers.