02-11-2014, 06:03 AM | #15 |
Sellin Chevy's since '06
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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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02-11-2014, 07:09 AM | #16 |
Drives: 1970-1/2 Z-28, 2017 ZL1 Join Date: Sep 2012
Location: Sanford, Fl
Posts: 973
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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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02-11-2014, 09:36 AM | #17 |
Drives: '15 SS 1LE, '69 Z28 drag car Join Date: Dec 2009
Location: Mich
Posts: 4,482
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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. |
02-11-2014, 10:31 AM | #18 | |
Drives: Ferrari F430 Spider F1 Azzurro Arge Join Date: Sep 2013
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Quote:
http://en.wikipedia.org/wiki/Galling |
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02-11-2014, 05:56 PM | #19 | |
Runs with scissors...
Drives: '14 Z/28s SIM/SW Join Date: Jan 2013
Location: Austin, TX
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Quote:
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02-11-2014, 06:21 PM | #20 | |
Drives: 2013 Triple Black ZL1 / 2006 TB SS Join Date: Feb 2011
Location: MN
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Quote:
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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02-11-2014, 06:47 PM | #21 | |
Drives: Ferrari F430 Spider F1 Azzurro Arge Join Date: Sep 2013
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Quote:
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02-11-2014, 07:36 PM | #22 | |
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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. Last edited by Skylane765; 02-11-2014 at 07:54 PM. |
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02-16-2014, 12:26 PM | #23 |
Drives: 1932 pro street truck ZO6 LS7 power Join Date: Jan 2011
Location: Greenbrier tenn & pennington gap VA.
Posts: 118
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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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02-16-2014, 01:23 PM | #24 | |
Drives: 1970-1/2 Z-28, 2017 ZL1 Join Date: Sep 2012
Location: Sanford, Fl
Posts: 973
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Quote:
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02-16-2014, 01:31 PM | #25 | |
Drives: 14 Z/28 0# Join Date: May 2013
Location: NY
Posts: 773
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Quote:
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02-17-2014, 01:29 AM | #26 |
Runs with scissors...
Drives: '14 Z/28s SIM/SW Join Date: Jan 2013
Location: Austin, TX
Posts: 1,439
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And I'm pretty certain it throws your factory engine warranty out the window...
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02-17-2014, 06:38 AM | #27 |
Drives: 1932 pro street truck ZO6 LS7 power Join Date: Jan 2011
Location: Greenbrier tenn & pennington gap VA.
Posts: 118
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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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02-17-2014, 10:09 AM | #28 | |
Drives: 2006 Z06 Join Date: Oct 2010
Location: Gilbert, AZ
Posts: 5,712
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Quote:
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Nick
Corvette Z06 -1200ish rwhp |
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