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LS7 Valve Issues

 
Old 03-10-2019, 06:05 PM
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ramaccc
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Default LS7 Valve Issues

Question re: LS7 valve issues

So I'm sure it has been discussed several places which I haven't been able to find as of yet. My question is I have a 2012 Z06 that has full extended factory warranty until 2021 or 60K. I'm not having any valve issues as of now however wanted to know if this issue is something that is covered under warranty. If it is will GM perform repairs even before the issue becomes a concern?

Any info would be appreciated.

Mike
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Old 03-10-2019, 06:38 PM
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03BlkZ
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If you have the warranty then wait until it's about to expire and have GM do a check of the guides. When they find them out of spec because they will have them give you new heads and send them to AHP to get fixed before having them install them on your car. Also all you have to do is use the search function and look for valve guides and you will find a ton of threads. People here seem to get irritated by valve guide/head posts. Good luck!
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Old 03-11-2019, 10:23 AM
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Undy
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You will have to pay your dealer to pull the heads and inspect the valves/guides. If they say they're fine then you'll be on the hook for around $2K +/- for their work. GM pulled back their "wiggle test" as a non-sanctioned check. If it were me I'd either do the wiggle test myself or pay an independent shop to accomplish it first. If the valve guides are suspect then I'd have some level of confidence giving them to the GM dealer to accomplish the work.
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Old 03-11-2019, 11:04 AM
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If it's still under warranty I'd wait for it to show signs of a problem since their not going to look at it until that happens. GM and most companies now a days don't really believe in real preventive maintenance.
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Old 03-11-2019, 02:55 PM
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BigVette427
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The flip side of waiting is that if you drop a valve and blow a hole in your block, you're going to need an entire new engine, so check your policy and see how much they cap warranty work per incident, and lifetime. The only way you will know if your valve guides are in spec is if you take your heads off and measure them, which at that point, you may as well have your heads rebuilt and put new guides in anyways. The wiggle test is better than nothing, but last I heard GM wasn't accepting that for warranty purposes any longer.
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Old 03-11-2019, 03:13 PM
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Never seen a warranty fix something preventively. You need to show that something is wrong. So wait for it to fail, or you have to pay for inspection, and once it is shown to be a failure, warranty should cover it all.

As for "the only way" is to pull heads and measure, I disagree with that. Wiggle test may not indicate difference between .030" and .025" but if the valve flops back and forth 1/4" you don't have to pull a head to know right away it is WAY beyond the limit. It will show gross failures easy enough, what it doesn't show is borderline conditions.

Last edited by Unreal; 03-11-2019 at 03:14 PM.
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Old 03-11-2019, 05:20 PM
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The other problem is that if you take the car to the dealer, and they agree to replace the heads...you typically just get another set of suspect GM (linamar assembled) heads. Unless you have one of those rare GM dealers like Able Chevy in NorCal that will install AHP heads with most extended warranties.

What warranty company is it OP?
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Old 03-11-2019, 06:09 PM
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Hib Halverson
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"Wiggle testing" is only good for determining if stem-to-guide clearance is "way" in spec or "way" out of spec. It cannot determine with any accuracy if guide clearance is "just under" or "just over" GM's maximum for guide clearance. The only way to do that is remove and disassemble the heads then measure stems with a mic, guides with a bore gauge then "do the math."

One of the problems with this who valve guide issue is that GM's specification for valve seat runout is pretty high, so, if a new set of heads has runout much more than .001 per valve, you'll likely just experience the problem again.

I had the heads replaced on my 2012. They came to the dealer as two castings and two boxes of parts. I took them to my own cylinder head shop (now retired unfortunately) and had the run out checked only to find that there were some seats in the new heads which were worse than those in the old heads. That shop fixed the runout problem then assembled the replacement heads and my dealer installed them.

With respect to stock or near stock LS7 heads, if you have a guide wear issue, once that is repaired, make sure valve seat runout is .0005-.0010 and future guide durability will be insured. Anyone who knows there way around a Serdi or a Newen ought to be able to get close to "five tenths" for runout

If you are in Northern California, absolutely, go see Abel Chevrolet. They people there understand Corvettes and LS7s.
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Old 03-11-2019, 06:19 PM
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For example, you can't tell visually if a tire is at 28psi or 30psi, but you can tell if it has a blow out, or is completely flat. A wiggle test is like that, if it is so bad the exact measurements don't really matter. Just like if a tire has 0-2psi, and rim is sitting on the ground, you don't need a gauge to tell you the tire pressure is low.
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Old 03-13-2019, 03:22 PM
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Keep close check of oil consumption. At 40k miles, my previous Z06 ate a quart every 300 to 400 miles. Indy shop did wiggle test and GM accepted their findings. Seems oil consumption is the first major indicator.
Irony for me was after all the work was done, a drunk hit the car and totaled it. Crying shame.
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