[Z06] Video LS7 Wear Exhaust Valves
03-29-2013, 02:55 PM
#81
One expert in the area said that GM was having issues maintaining proper LS7 oil film thickness with its corporate mandated requirement to use 5w30 oil and solved the issue by reducing the weight of the rods.
A few things to consider here:
What would the weight be for a LS7 size solid valve vs. Part #12586484?
Rev limit for the other motors vs LS7?
Ramp rates / duration / lift for the cams used?
I've posted in a few of these topics I don't see Stainless Valves being a problem, if you can set the spring pressures to handle the heavier valves. You may also run into a situation where the valve springs should be changed more often but it is easier to change springs than guides and valves.
GM has their reasons and their durability testing which goes far beyond what vast majority of us will ever see. Why did GM run titanium rods? The aftermarket has been building 427s with heavier rods long before GM built the LS7 and they were reliable.
What would the weight be for a LS7 size solid valve vs. Part #12586484?
Rev limit for the other motors vs LS7?
Ramp rates / duration / lift for the cams used?
I've posted in a few of these topics I don't see Stainless Valves being a problem, if you can set the spring pressures to handle the heavier valves. You may also run into a situation where the valve springs should be changed more often but it is easier to change springs than guides and valves.
GM has their reasons and their durability testing which goes far beyond what vast majority of us will ever see. Why did GM run titanium rods? The aftermarket has been building 427s with heavier rods long before GM built the LS7 and they were reliable.
03-29-2013, 03:00 PM
#82
This was my point ...
The stock LS3 exhaust valve from the information I can find is 89g
http://www.yellowbullet.com/forum/sh...60&postcount=8
The Rev Extreme X1137 exhaust valve sometimes used in these LS7 SS modifications is 98g
And I should point out that when I responded to that post, I was only responding to just the general statement; "Solid stem SS exhaust valves were too heavy for beehive springs" made by hapnermw.
But the point he may have been trying to make in that post, could be that a beehive spring would not be suitable in an LS7 using heavier valves, would be verified by the spintron testing in the GM High Tech Performance article of awhile back.
http://www.gmhightechperformance.com...er_system.html
http://www.yellowbullet.com/forum/sh...60&postcount=8
The Rev Extreme X1137 exhaust valve sometimes used in these LS7 SS modifications is 98g
And I should point out that when I responded to that post, I was only responding to just the general statement; "Solid stem SS exhaust valves were too heavy for beehive springs" made by hapnermw.
But the point he may have been trying to make in that post, could be that a beehive spring would not be suitable in an LS7 using heavier valves, would be verified by the spintron testing in the GM High Tech Performance article of awhile back.
http://www.gmhightechperformance.com...er_system.html
03-29-2013, 03:02 PM
#83
Team Owner
I've read that as well. Thus my comments about GM's requirements.
Last edited by 93Polo; 03-29-2013 at 03:28 PM.
03-29-2013, 03:02 PM
#84
You guys who just got in here, in warranty, and whom it pains to believe that you paid hard earned money for a car with an engine in it which might have a serious flaw, are an interesting lot.
Anyone who tells you that everything is alright, you are 100% down with them.
Makes you feel better, as nobody wants to believe that they bought something, something which they have dreamed about, but which might have a serious flaw in it.
As such, you vilify any who tell you that, and champion those who tell you what you want to hear and "reassure" you that you didn't buy something which might have a flaw in it.
Just asking here, but Vette@71, is this your first Vette, and did you not get it until you turned 71?
Anyone who tells you that everything is alright, you are 100% down with them.
Makes you feel better, as nobody wants to believe that they bought something, something which they have dreamed about, but which might have a serious flaw in it.
As such, you vilify any who tell you that, and champion those who tell you what you want to hear and "reassure" you that you didn't buy something which might have a flaw in it.
Just asking here, but Vette@71, is this your first Vette, and did you not get it until you turned 71?
03-29-2013, 03:06 PM
#85
Burning Brakes
More wild assed assumption from you. Making a living, and making a living to support a particular way of life that one has grown accustomed to are two different things. I would not start making assumptions about me, what I know or don't know, or what I can do or not do, from what I write on this sight.
I didn't say this crowd is "stupid", but you sure as hell just did.
I didn't say this crowd is "stupid", but you sure as hell just did.
Last edited by ramairws6; 03-29-2013 at 03:12 PM.
03-29-2013, 03:11 PM
#86
Team Owner
I disagree that the valve is the root cause of the problem. No more, no less. Actually I disagree with the conclusion that the valve is the root cause since there is no evidence or rational engineering explanation.
It fries my brain that some can claim the valve is the root cause with no evidence whatsoever, so I guess we're even
My personal stake in the matter has nothing to do with my intellectual analysis of the matter. Of course there is something causing the guides to wear out. We just don't know what (yet), at least not with 100% certainty.
It fries my brain that some can claim the valve is the root cause with no evidence whatsoever, so I guess we're even
My personal stake in the matter has nothing to do with my intellectual analysis of the matter. Of course there is something causing the guides to wear out. We just don't know what (yet), at least not with 100% certainty.
Honestly after reading in here for a year, it is hard to make a conclusion other than their seems to be a problem somewhere on some cars. Stainless valves and bronze guides are proven technology. Many believe that titanium has durability concerns on the exhaust side.
Do you think there is a problem and if so what is the likely root cause?
03-29-2013, 03:12 PM
#87
Drifting
I enjoy reading Mark's and Quick's views. I hope everyone can remain civil but it's nice to see different viewpoints and make your own decision.
I don't find anyone annoying.
I myself decided to stay away from a GM head casting in totality and did a PRC casting with Ti intake and SS exhaust. Can't wait to get everything installed.
I don't find anyone annoying.
I myself decided to stay away from a GM head casting in totality and did a PRC casting with Ti intake and SS exhaust. Can't wait to get everything installed.
03-29-2013, 03:18 PM
#88
Honestly after reading in here for a year, it is hard to make a conclusion other than their seems to be a problem somewhere on some cars. Stainless valves and bronze guides are proven technology. Many believe that titanium has durability concerns on the exhaust side.
Do you think there is a problem and if so what is the likely root cause?
Do you think there is a problem and if so what is the likely root cause?
03-29-2013, 03:21 PM
#89
Burning Brakes
You guys who just got in here, in warranty, and whom it pains to believe that you paid hard earned money for a car with an engine in it which might have a serious flaw, are an interesting lot.
Anyone who tells you that everything is alright, you are 100% down with them.
Makes you feel better, as nobody wants to believe that they bought something, something which they have dreamed about, but which might have a serious flaw in it.
As such, you vilify any who tell you that, and champion those who tell you what you want to hear and "reassure" you that you didn't buy something which might have a flaw in it.
Just asking here, but Vette@71, is this your first Vette, and did you not get it until you turned 71?
Anyone who tells you that everything is alright, you are 100% down with them.
Makes you feel better, as nobody wants to believe that they bought something, something which they have dreamed about, but which might have a serious flaw in it.
As such, you vilify any who tell you that, and champion those who tell you what you want to hear and "reassure" you that you didn't buy something which might have a flaw in it.
Just asking here, but Vette@71, is this your first Vette, and did you not get it until you turned 71?
Not surprising at all..
You are a great Archivist however..
03-29-2013, 03:23 PM
#90
Team Owner
But the point he may have been trying to make in that post, could be that a beehive spring would not be suitable in an LS7 using heavier valves, would be verified by the spintron testing in the GM High Tech Performance article of awhile back.
http://www.gmhightechperformance.com...er_system.html
http://www.gmhightechperformance.com...er_system.html
I would not expect a spring GM spec'd for a hollow valve to support a stainless valve. If you change one factor, then the entire package must be considered.
I'm not a fan of beehives. It goes back to when I did H&C, there was a batch of Comp 918s that had problems. With a single if it breaks you have very little to keep it from hitting the piston. When I did heads I went with TEA because they came with larger Comp 987 doubles. The heads must be machined for the larger spring. The 987s were cheaper to change and IMO offer more insurance should a spring fail in any way. Spring choice was limited at the time for LS drop in replacements. I am not an expert but the combination under my ownership and the current owner has proved durable.
03-29-2013, 03:26 PM
#91
Otherwise, you're just blowing smoke.
And yes, I know that I am a great archivist. Let me show you how great.
You're 5 months into ownership of this vehicle. And immediately after that purchase, you were looking for reassurances that everything was alright when you posted up this thread.
http://forums.corvetteforum.com/c6-z...post1582060744
And since that time of purchase, you have lashed out at anything, or anyone, indicating that all might not be right with the LS7 valve train.
http://forums.corvetteforum.com/c6-z...post1582081024
Only thing I was wrong about so far, was that it was "stock". Which makes it even more interesting.
Because it's not stock, and is out of warranty due to the tune, you want even more for the valve issue to be overblown.
Anything, or any attempt, to indicate that it isn't, invades your comfort zone.
Because it is out of warranty, due to that tune, you know that you are " butt naked", and in the wind, and do not want to hear that you are at risk. The "ostrich" approach.
If it fails, well, you get to pay out of pocket. After just laying out a load of dough for it. You don't want to think about how likely that might be. And anyone informing you that it might be, is your enemy.
350Z before, graduating to a Vette, right?
http://forums.corvetteforum.com/nort...post1582283840
Now here were a couple more interesting posts.
http://forums.corvetteforum.com/c6-z...post1582467938
http://forums.corvetteforum.com/c6-z...post1582542359
BTW, what are your thoughts on "geometry" and it's role in this matter since that bigtop thread back around Thanksgiving?
:
Last edited by '06 Quicksilver Z06; 03-29-2013 at 03:57 PM.
03-29-2013, 03:35 PM
#92
Burning Brakes
03-29-2013, 03:38 PM
#93
Team Owner
03-29-2013, 03:39 PM
#94
The only other possible root causes, setting aside witchcraft 
, is driver abuse (including lack of maintenance) or engine modifications.
Since it is a fact that GM is now replacing some percentage of the LS7 heads brought in for their valve wiggle test, GM themselves has verified accelerated valve guide wear is an issue with non-abused, non-modded engines.
The only possible root cause is an LS7 valve train design and/or materials issue.
The fact that most LS7s with this issue haven't broken an exhaust valve is actually a credit to the strength of the sodium filled valve. It is being subjected to torture-testing well beyond its normal operational envelope in thousands of LS7s daily.
, is driver abuse (including lack of maintenance) or engine modifications. Since it is a fact that GM is now replacing some percentage of the LS7 heads brought in for their valve wiggle test, GM themselves has verified accelerated valve guide wear is an issue with non-abused, non-modded engines.
The only possible root cause is an LS7 valve train design and/or materials issue.
The fact that most LS7s with this issue haven't broken an exhaust valve is actually a credit to the strength of the sodium filled valve. It is being subjected to torture-testing well beyond its normal operational envelope in thousands of LS7s daily.
03-29-2013, 03:42 PM
#95
Team Owner
GM's goal wasn't to use sodium valves. Their goal is to safely contain and distribute that heat.
GM used the approach of using a sodium filled hollow valve and I surely wouldn't want to replace it with another hollow valve of similar mass without that sodium to contain heat and aid in distribution. Clearly the sodium served a purpose in the implementation GM moved forward with.
In that scenario, yes, I wouldn't want to run a non-sodium filled valve.
However, that doesn't mean another approach cannot also be correct.
In a hollow stem, all the heat is contained within the thin valve stem walls. A solid stem with more mass will be able to contain more heat and because it has some actual 'depth' it may result cooler valve stem walls with a warmer 'center'.
The valve stem on a solid valve may be cool enough not to cause the galling and burn marks we've seen on the OE hollows. Simply put, it just contains and distributes the heat better.
GM used the approach of using a sodium filled hollow valve and I surely wouldn't want to replace it with another hollow valve of similar mass without that sodium to contain heat and aid in distribution. Clearly the sodium served a purpose in the implementation GM moved forward with.
In that scenario, yes, I wouldn't want to run a non-sodium filled valve.
However, that doesn't mean another approach cannot also be correct.
In a hollow stem, all the heat is contained within the thin valve stem walls. A solid stem with more mass will be able to contain more heat and because it has some actual 'depth' it may result cooler valve stem walls with a warmer 'center'.
The valve stem on a solid valve may be cool enough not to cause the galling and burn marks we've seen on the OE hollows. Simply put, it just contains and distributes the heat better.
DH
03-29-2013, 03:50 PM
#96
03-29-2013, 04:00 PM
#97
The only other possible root causes, setting aside witchcraft , is driver abuse (including lack of maintenance) or engine modifications.
Since it is a fact that GM is now replacing some percentage of the LS7 heads brought in for their valve wiggle test, GM themselves has verified accelerated valve guide wear is an issue with non-abused, non-modded engines.
The only possible root cause is an LS7 valve train design and/or materials issue.
The fact that most LS7s with this issue haven't broken an exhaust valve is actually a credit to the strength of the sodium filled valve. It is being subjected to torture-testing well beyond its normal operational envelope in thousands of LS7s daily.
, is driver abuse (including lack of maintenance) or engine modifications. Since it is a fact that GM is now replacing some percentage of the LS7 heads brought in for their valve wiggle test, GM themselves has verified accelerated valve guide wear is an issue with non-abused, non-modded engines.
The only possible root cause is an LS7 valve train design and/or materials issue.
The fact that most LS7s with this issue haven't broken an exhaust valve is actually a credit to the strength of the sodium filled valve. It is being subjected to torture-testing well beyond its normal operational envelope in thousands of LS7s daily.
with you 100%.Well thought out, well stated, and accurate post.
03-29-2013, 04:07 PM
#98
Drifting
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what kind of evidence can I post? I can't make one pop in front of you. it's a heating issue an can be seen on the valve stem, anyone that works on cylinder heads can see this. I have checked the ls7 heads from top to bottom. the evidence is being posted in front of you almost daily and how many z06 owners are here 200?300?400? that should tell you something, if you have valve guide wear like showed in these vids it's just a matter of time till it breaks. I know what it is, but it wouldn't matter what I post. mybe some of you looking for the "fix" and are not happy with my findings can call some cylinder head shops and ask them. the truth hurts trust me, I went though it. in the end it's up to you guys I've done my best.
03-29-2013, 04:15 PM
#99
Team Owner
DH
03-29-2013, 04:18 PM
#100
Burning Brakes
your number 1 on my list. I'm at work working on a set of heads. when you figure out the issue let me know. I will not be rude to ppl on this forum. if you disagree fine do what you want with your car I'm not gonna strong arm you to do anything. what I'm trying to do is show ppl what to look for, how things work ect. the heads are having issues I think we all agree to that.look at all the ppl with bad guides,look at how many ppl have bought prc heads in just the last few weeks...
Hey Chad, Brodix BR7 heads for me...Just deliveerd from Richard at WCCH...Will post up some pics of the heads soon...They are soooo perty...