skywalker

14k might be a little optimistic. Just checked my 2011 with 5k on it . exhaust are OK, not great but the intake guides over spec.

Mark2009

Damn

AzDave47

... but they started 100% inspection with Feb 2011 builds, how could that be?

Mark2009

Probably because a 2011 car was likely built in the last half of 2010.

Secondly because while roughness of the intake valve stem is already a known issue (causing wear on that guide, altho seemingly not fatal wear), it may not be one that GM has addressed (or if it is, the time frame is unknown).
.

Hib Halverson

About three weeks ago, GM issued a bulletin about valve guides. See:
http://forums.corvetteforum.com/c6-z...post1583058928

JetBlue427

that bulletin was posted by a GM tech on this forum a few weeks ago

1badtantrum

The individual pieces are being looked at. It seems the valves would be exposed to some stresses/wear beyond what they were intended and I expressed my thoughts and the dealer was going to review it with GM. I feel that they will replace what needs to be replaced.

1badtantrum

I will actually check the valve guides in about 10K-12K miles or before if the noise gets more noticeable or oil analysis shows higher than normal iron content. It's relatively easy and I'm glad to know that there is something additional I should check. I had the car to a few HPDE's over the past few years. The oil analysis actually indicated a bit of 'remarkable' iron content. I would expect a bit more wear than average under those stresses.

Mark2009

Please keep us posted... I'm currently negotiating with my dealer on getting mine checked, but if GM shows a pattern of not replacing the complete cylinder head assembly as a unit then I'll have it done elsewhere on my dime.

1badtantrum

I didn't gather this from your first comment, but I think what you say is fair. I'm not sure what the problem is/was with my heads. I'm interested in understanding how the new heads/guides wear. I plan on attending at least one HPDE later this year. I will change the oil before and after as always. I'll have the oil analyzed. If there is higher than 'normal' iron content, I'll make note and check the guides at some interval down the road. Having the car at a few HPDE's exerts some stresses far beyond what is normal. I'm not sure if those stresses alone are enough to cause the guide wear I had. There certainly are a number of opinions on the valve guide wear.

1badtantrum

I've contemplated this very thing... If your still under wty, why not have it fixed however GM/dealer decide how to fix it and continue to enjoy your car under wty. Then, when you near the end of your wty, go off the reservation and have the heads worked to your standards?
This is what I've decided to do. I'm anxiously awaiting Katech test results.

Mark2009

Because I do not know if they are competent. So far the jury is leaning towards no. I would barely trust them to replace the heads as assemblies, and even then I'd like to monitor the operation. To disassemble and reassemble and mix-and-match used valves and springs and retainers? No way. And as others have noted, I'm not sure the original exhaust valves should be reused in any case (they'd need to be closely examined).

Mr. Goodwrench:
Ideally this is a job that should only need to be done once.
.

jedblanks

14,000 (at fix)+ 14,000 (after fix)= 28,000 (total) "Befuddling" math for sure.
Thanks for making my point -- the same one you found without merit.

I would to propose to all parties that this issue is the guides. Pure and simple. They aren't long enough. Replacing them with longer bronze versions (or oem material if you can find it) WILL fix the issue.

Stainless and the requisite new springs might make you sleep better at night, but if the guide wears, the valve will hit off center, stretch, then break no matter the valve material.

Keeping the stock valves allows you to keep the stock valve spring setup.

Katech knows its true, GM knows its true. Read between the lines.

jimman

I must have short guides, 165,000 and tight

jedblanks

Have you measured your guide clearance? Curious to know what it is. Good data point.

jimman

Judgement call, couldn't see a problem with stems, even if they were close to max, I'll make it. Leak down and compression all within spec, plugs dry, no smoke on startup. Engine sounds the same as it did when new, no complaints. Coming up on a cross coutry trip again, 8000 miles may need a tow who knows. Am a bit concerned about Alternator seems I'm in the mileage range. Sure has been a fun ride, Jim Hall tuned it when it had 110 miles. Only problem is having to replace tires, got set 16 ready to go on before May's trip.

PAmotorman

how many owners with this problem are no longer using Mobil 1 ???

Kanf

I have a 2013 427 purchased in Dec of 2012. How do I check my engine build date? and or, do you all think I would even need to worry about this or have the dealer check mine? I have noticed some valve type noise coming from the engine but it may be normal.

I searched for the Service bulletin but cannot find it in this big thread. Could someone please post it here in case I need to take mine in for inspection.

Thanks

X25

If GM indeed fixed the issue back in Feb 2011, you're not supposed to have the issue. LS7 valve-train and also its injectors are noisy by design; the noise is probably normal, and does not indicate any issue. There is another thread where a video with the stock LS7 idling is recorded on a video. If you have doubts, that video might be a good comparison.

Actually, here is that thread:
http://forums.corvetteforum.com/c6-z...ock-heads.html

Mark2009

Bulletin is here: http://forums.corvetteforum.com/c6-z...n-from-gm.html

Build date is encoded on a bar code sticker on driver side head behind alternator/ps pump (or thereabouts), but it is generally close to the build date of the car (driver door latch). I don't think it is relevant in your case.