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Old 02-11-2014, 06:03 AM   #15
davidcroft
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The issue is specifically with the titanium intake valves. I saw an 06 that had been rocking a cam for a while (and not a good spec'd cam) and he pulled the heads to get them ported and get a good spec'd cam for his motor. The intake valves had so much play in the head it was ridic. But yes they call it valve stem guide wear and I'm not sure in GM engineers know what's causing this issue, or if they're even admitting it's an issue. I do know that this issue has arisen in the past couple of years and the LS7 has been out since about Feb of '06. Like all issues it won't affect every car. Like hognutz said, you can pull the rocker cover and see if they're making proper contact.

I do know that if you're thinking about modding a Z/28, you can be willing to bet GM won't be as mod friendly on the service side. Those LS7s are expensive and motor claims will probably trigger a field engineer to inspect.
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Old 02-11-2014, 07:09 AM   #16
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is there a noise the comes on and let's you know the problem happening before failure? I am monitoring the S/C coupler noise in my ZL1 which is very minimal at this point but is there something similar you can listen for in the LS7 valve train, like a lose rocker?
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Old 02-11-2014, 09:36 AM   #17
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If you want to be proactive.... Use great oil. Something like an Amsoil. And be careful with the break in.

A lot of valve to valve guide wear occurs during break in. Especially if that clearance is a hair on the tight side when green new. The seals are new, the parts are tight... there won't be much oil lube in there, and lots of heat. Recipe for galling if pushed hard when green.

So many people talk about driving brand new engines like they stole them. Trouble is, if there is a valve stem a bit snug it will gall like crazy.. and that starts the premature wear. Break it in easy and let the valve stems and guides get to know each other gives it a much better chance at maintaining proper clearances. Not super easy, just normal driving, moderate varying loads.

Info is from a neighbor who works in powertrain dyno testing for one of the big three. Tells me all the time about what happens when a green engine is thrashed wide open. Most survive... but if one has a tight valve or a tight piston... bad things happen. That same engine with parts a hair too tight, if broken in easy will be just fine.
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Old 02-11-2014, 10:31 AM   #18
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Originally Posted by Russell James View Post
If you want to be proactive.... Use great oil. Something like an Amsoil. And be careful with the break in.

A lot of valve to valve guide wear occurs during break in. Especially if that clearance is a hair on the tight side when green new. The seals are new, the parts are tight... there won't be much oil lube in there, and lots of heat. Recipe for galling if pushed hard when green.

So many people talk about driving brand new engines like they stole them. Trouble is, if there is a valve stem a bit snug it will gall like crazy.. and that starts the premature wear. Break it in easy and let the valve stems and guides get to know each other gives it a much better chance at maintaining proper clearances. Not super easy, just normal driving, moderate varying loads.

Info is from a neighbor who works in powertrain dyno testing for one of the big three. Tells me all the time about what happens when a green engine is thrashed wide open. Most survive... but if one has a tight valve or a tight piston... bad things happen. That same engine with parts a hair too tight, if broken in easy will be just fine.
Thanks for great insights. Some more info here:

http://en.wikipedia.org/wiki/Galling
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Old 02-11-2014, 05:56 PM   #19
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...So many people talk about driving brand new engines like they stole them. Trouble is, if there is a valve stem a bit snug it will gall like crazy.. and that starts the premature wear. Break it in easy and let the valve stems and guides get to know each other gives it a much better chance at maintaining proper clearances. Not super easy, just normal driving, moderate varying loads...
I've never understood guys who believe that breaking in a car hard and fast results in a faster car. Engineers aren't stupid, and engines need time for all the parts to bed in and settle down. Though it will be painful, I'm willing to baby my Z/28 and break it in softly and slowly -- and then I'll track the hell out of it...
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Old 02-11-2014, 06:21 PM   #20
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Originally Posted by mkorgan View Post
is there a noise the comes on and let's you know the problem happening before failure? I am monitoring the S/C coupler noise in my ZL1 which is very minimal at this point but is there something similar you can listen for in the LS7 valve train, like a lose rocker?

Valve train noise is one way; but there is a specific way to measure the valve play (called the wiggle test) as noted in TSB. If you read the other corvette forum; there is a ton of information on this subject. One would think GM has addressed this on the Z/28 because the internal engine components are different and this is really the only knock on an otherwise great motor. With that said, I would not hesitate running the car to redline if I owned either car.
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Old 02-11-2014, 06:47 PM   #21
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Valve train noise is one way; but there is a specific way to measure the valve play (called the wiggle test) as noted in TSB. If you read the other corvette forum; there is a ton of information on this subject. One would think GM has addressed this on the Z/28 because the internal engine components are different and this is really the only knock on an otherwise great motor. With that said, I would not hesitate running the car to redline if I owned either car.
Perhaps one of the unofficial official GM people could throw us a bone and make an unofficial clarification comment here . . . .
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Old 02-11-2014, 07:36 PM   #22
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Perhaps one of the unofficial official GM people could throw us a bone and make an unofficial clarification comment here . . . .
Yes, that's what I recommend. Maybe even a copy of the service bulletin.
That would help.

We do the wiggle test on Lycoming engines because of the valve being too tight.

It is also common for a factory to do a fix but not let it be known because all the prior owners may want that fix and not need it in reality, being only a few were affected. Now if a safety issue, that would have to be addressed on all known cars.

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Old 02-16-2014, 12:26 PM   #23
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Ok guys... I own a LS7 motor. I have it in a 1932 ford pro street truck. The Exhaust valves, And all the valve guides are the problem. I have done, a lot of research, on this problem. The best advice, I can give you, is to do what so many of us LS7 owners have done. Send the heads off to WCCH, That's west coast cylinder heads. Have all new valve guides installed. And remove the sodium exhaust valves. Replace them with stainless exhaust valves. This seams to fix the problem. I have not heard of anyone having any problems, after doing this to the LS7 heads. That includes me.
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Old 02-16-2014, 01:23 PM   #24
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Ok guys... I own a LS7 motor. I have it in a 1932 ford pro street truck. The Exhaust valves, And all the valve guides are the problem. I have done, a lot of research, on this problem. The best advice, I can give you, is to do what so many of us LS7 owners have done. Send the heads off to WCCH, That's west coast cylinder heads. Have all new valve guides installed. And remove the sodium exhaust valves. Replace them with stainless exhaust valves. This seams to fix the problem. I have not heard of anyone having any problems, after doing this to the LS7 heads. That includes me.
And how much does this cost if you don't mind sharing?
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Old 02-16-2014, 01:31 PM   #25
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Originally Posted by Russell James View Post
If you want to be proactive.... Use great oil. Something like an Amsoil. And be careful with the break in.

A lot of valve to valve guide wear occurs during break in. Especially if that clearance is a hair on the tight side when green new. The seals are new, the parts are tight... there won't be much oil lube in there, and lots of heat. Recipe for galling if pushed hard when green.

So many people talk about driving brand new engines like they stole them. Trouble is, if there is a valve stem a bit snug it will gall like crazy.. and that starts the premature wear. Break it in easy and let the valve stems and guides get to know each other gives it a much better chance at maintaining proper clearances. Not super easy, just normal driving, moderate varying loads.

Info is from a neighbor who works in powertrain dyno testing for one of the big three. Tells me all the time about what happens when a green engine is thrashed wide open. Most survive... but if one has a tight valve or a tight piston... bad things happen. That same engine with parts a hair too tight, if broken in easy will be just fine.
Great info! I have always followed the break in procedure on other cars. What is it on a new Camaro? 1000 miles varying rpms and never over 5k?
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Old 02-17-2014, 01:29 AM   #26
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And how much does this cost if you don't mind sharing?
And I'm pretty certain it throws your factory engine warranty out the window...
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Old 02-17-2014, 06:38 AM   #27
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And how much does this cost if you don't mind sharing?
I had it done about two years ago. And I think it was around, 7 to 8 hundred dollars. I race the truck on the drag strip, at nostalgia races & street drive it as well. No problems at all, since I had the work done.
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Old 02-17-2014, 10:09 AM   #28
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Awesome. I appreciate the fact this issue does not worry you. My brother-in-law has a LS7 in his vette and the dealer told him that there is nothing that they recommend to avoid the issue other than try to avoid high RPM ranges for extended periods of time. They acknowledged it is a known issue with a service bulletin associated with it but they do not do anything to proactively correct the problem as it effects less than 5% of the LS7 produced based on reported incidents. He laughed and said they recommended getting the extended warranty. Nice.
5% is way way way way low. I have seen 10 cars personally with the heads pulled off. 1 of them was within spec, and just barely at 20k miles. The other 9 were way out. I sold my motor to a go that dropped 2 valves, friend dropped a valve in front of me. Another friend dropped a valve. If it is only 5% then I have the unluckiest group of people around me.
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