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Originally Posted by Mark2009
(Post 1586756950)
To the contrary. Once the guides are worn out, the stems are unable to transfer the heat to the guide, which cooks the oil on the stem.
Since you clearly haven't gotten it yet, you tell us :D By the way, folks, ramair's post was plagiarized, verbatim, from a four-year-old post by someone else on another forum: http://ls1tech.com/forums/13450863-post12.html . I clearly read his remark as pertaining to the quote he posted without properly using the quote function. :cheers: DH |
Originally Posted by Wass
(Post 1586757280)
I wouldn't have known because he's on my ignore list.
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For all who are interested, here is the entire quote from Richard@WCCH.... I think it's interesting stuff!
We have definitely seen excessive wear in some LS7 exhaust guides. Mostly coming from engines with over 30k on the clock. We have seen some heads show inconsistent wear requiring only one or two guides needing replacement. It appears that the sodium exhaut valves are transmitting an excessive amount of heat from the stem to the guide. In some cases the oil is BBQ'd in the guide and the lack of lubrication and cooling from the oil causes the excessive wear (mostly in the lower half of the exhaut guide). We've measured some guides as having over .004" of wear in the lower 1" of exhaust guide length. Porsche 911's suffer the same type of related guide wear on the exhaust side. The next item to note regarding the sodium exhaust valves relates to the wall thickness of the sodium exhaust valve stem. It's only .040" thick and makes for a fragile exhaust valve. GM uses a good quality steel material but the design spec. renders the valves brittle at the neck. Hence the reason we choose the replace the factory units with stainless or inconel. The exhaust valves we use are manufactured with a .001" oversized stem size which allows us to hone the exhaust guides and remove most or all of the taper in the bore. In cases with excessive wear we replace the guides with bronze. I can't comment on weather the excessive guide wear is causing the valves to rattle around in the guide on on the seat causing the head failures. It may be due to excessive heat buildup from the restricted heat flow path to the guide. As I mentioned before, there's only 1mm of wall thickness at the valve neck. Not a good situation in engines producing high specific horespower. The stainless exhaust valves don't show the rapid wear that the sodium valves have. Given the same conditions, the bronze guides will wear as well. The size of the small heat path must be increased. With a solid stem valve heat is allowed to travel further up the length of the stem. It provides a larger flow path for heat dissipation. The primary heat path is through the valve seat. The secondary heat path is through the valve guide. Lean stoic. conditions at cruising speeds generate lots of heat on the exhaust valves with unleaded fuels. The heat bakes the small amounts of oil that makes it to the lower portion of the exhaust guide. Once the lubrication is gone there is metal to metal contact and on a molecular level electron sharing occurs. The steel molecues of the exhaust valve stem have a greater resistance to wear. The powdered metal guides have mixture of wear resisting alloys along with lubritious properties pressed into the matrix. You don't have to beat on the engine to experience valve guide wear. The primarly reason we use bronze valve guides is because GM will not sell the guides separately. Rather they will sell you an entire replacement head. The aftermarket parts supply only furnishes bronze alloy valve guides. I personally like the powdered metal valve guides the factory uses but the supplier does not sell piece meal to the public. Additionally we have no long term wear issues with the bronze guides and solid stem stainless steel valves. In the last decade GM has done a masterful job improving both metalurgy and rocker arm geometry to reduce overall valve guide wear. Rocker arm desings are also superbly executed. The issues seem to only be related to the sodium valves. |
Yes, I am running them. Over 3000 miles on them so far. And I don't limit the redline.
:cheers: |
Originally Posted by NavyAirTraffic
(Post 1586761027)
For all who are interested, here is the entire quote from Richard@WCCH.... I think it's interesting stuff!
What I have a hard time understanding is, when someone makes huge profits from an issue like this, why any intelligent individual would simply take the word of that guy who's making all the money. At best it is just one man's opinion, at worst it is an opinion which is tainted to ensure his profits are maximized. The more you can undermine confidence in GM's engineering the more money you will make...heck you'll even get lemmings who will 'fix' their heads when they aren't even 'broken' in the first place, just have to convince everybody about how 'weak' them stock valves are :ack: Cheers, Paul. |
And you will also get the biggest fools who think that people can watch these stock valves fail time and again, and not take notice of it and advocate business as usual when it comes to this matter.
I'm hoping that there is no one at GM, or in here for that matter, like that though. |
Originally Posted by '06 Quicksilver Z06
(Post 1586761397)
And you will also get the biggest fools who think that people can watch these stock valves fail time and again, and not take notice of it and advocate business as usual when it comes to this matter.
I'm hoping that there is no one at GM, or in here for that matter, like that though. |
Originally Posted by ramairws6
(Post 1586761681)
:lol: :lol: :D
The C5 column lock comes to mind. As does DBS and the crank pulley matter in the early C6s. I certainly hope that of those there who went along with business as usual in those instances, that there aren't others of the same ilk still there. Or anywhere else. But this below, is pretty strong and I edit my post here to include this following statement, only for the reason that I feel that it is liable to be removed from the individual who posted it. Normally I don't quote his tripe:
Originally Posted by MTIRC6Z
(Post 1586761247)
Given that GM is STILL using the sodium filled exhaust valve not only in the LS7 of the Z28 but also in the whole line of C7 Vettes, Richard has missed his calling, he could make MILLIONS from GM if he'd only share his wisdom. Just think of the huge engineering department budgets that could be eliminated by hiring Richard :rofl:
What I have a hard time understanding is, when someone makes huge profits from an issue like this, why any intelligent individual would simply take the word of that guy who's making all the money. At best it is just one man's opinion, at worst it is an opinion which is tainted to ensure his profits are maximized. The more you can undermine confidence in GM's engineering the more money you will make...heck you'll even get lemmings who will 'fix' their heads when they aren't even 'broken' in the first place, just have to convince everybody about how 'weak' them stock valves are :ack: Cheers, Paul. |
Originally Posted by '06 Quicksilver Z06
(Post 1586761397)
And you will also get the biggest fools who think that people can watch these stock valves fail time and again, and not take notice of it and advocate business as usual when it comes to this matter.
I'm hoping that there is no one at GM, or in here for that matter, like that though. Intake valves have failed too. Anyone who thinks the gm exhuast valves are the issues is in my opinion either ignorant, or just too stubborn to change a point of view after being mislead and misguided for a long time. |
Originally Posted by Blackonblacksls
(Post 1586761859)
Intake valves have failed too.
Anyone who thinks the gm exhuast valves are the issues is in my opinion either ignorant, or just too stubborn to change a point of view after being mislead and misguided for a long time. Do you know of more than that? If so, PM me as I try and keep track of the valve failures in here. Thanks. |
Originally Posted by Blackonblacksls
(Post 1586761859)
Intake valves have failed too.
Anyone who thinks the gm exhuast valves are the issues is in my opinion either ignorant, or just too stubborn to change a point of view after being mislead and misguided for a long time. |
Originally Posted by zcarbon
(Post 1586761950)
Wow Shady Inc. and his GF are over here too!:DDH
Spring is in the air :cheers: Bromances:rofl: |
Originally Posted by NavyAirTraffic
(Post 1586761027)
For all who are interested, here is the entire quote from Richard@WCCH.... I think it's interesting stuff!
[...] The size of the small heat path must be increased. With a solid stem valve heat is allowed to travel further up the length of the stem. It provides a larger flow path for heat dissipation. [...] The whole concept of a sodium filled valve is to move heat further up the length of the stem, away from the head of the valve. The quote above has it exactly backwards... in fact, the solid stem valve will let heat concentrate near the head. I would be wary about taking valve selection advice from someone who got such a basic concept so completely wrong. Following graphic from Manley, regarding heat distribution on a hollow sodium valve versus a solid titanium valve: The NexTek valve uses XH-428 stainless steel and a completely new manufacturing technique to create a valve with a hollow stem and head. The hollow sections of the valve are filled with sodium. The sodium provides an internal cooling mechanism for the valve, drawing heat away from the valve head. Read more: http://www.circletrack.com/enginetec...#ixzz307Cxdc6v |
Originally Posted by Mark2009
(Post 1586762487)
It is interesting, but sadly it is wrong.
The whole concept of a sodium filled valve is to move heat further up the length of the stem, away from the head of the valve. The quote above has it exactly backwards... in fact, the solid stem valve will let heat concentrate near the head. I would be wary about taking valve selection advice from someone who got such a basic concept so completely wrong. Following graphic from Manley, regarding heat distribution on a hollow sodium valve versus a solid titanium valve: ... How do you know which one is right? |
Interesting that anyone still thinks there is a valve issue in the LS7……..As has been posted, and as I have machine shop results showing, there is a machining problem in the LS7 head in terms of guides to valve seat alignment. Argument is old.
Argument about the hollow stem exhaust valve should center on the pros vs cons of such a valve. Not many cons in terms of "street" use. The LS7 intake valve is a nice piece. |
Originally Posted by WhiteDiamond
(Post 1586762716)
Interesting that anyone still thinks there is a valve issue in the LS7……..As has been posted, and as I have machine shop results showing, there is a machining problem in the LS7 head in terms of guides to valve seat alignment.
But the question remains as to if it is the case in "all", or even "most" of the examples of stock exhaust valve failure. No one has been able to answer that, because no one has looked. That's like being the coroner in a city, getting a call that a dead body has been found, and then automatically assuming that the person must have been stabbed or shot. Well how do you know, unless you look? |
Originally Posted by Blackonblacksls
(Post 1586761859)
Intake valves have failed too.
Anyone who thinks the gm exhuast valves are the issues is in my opinion either ignorant, or just too stubborn to change a point of view after being mislead and misguided for a long time. BUT you know what, IF I were making a really good living 'fixing' these heads but didn't actually know what was wrong in the first place and that I was basically just taking a shot in the dark that my work was going to last, I too might want to use a solid valve just in case my machine work didn't 'fix' the issue and the guides worn out again, you know kinda hedge my bets :ack: Then of course all you'd need is a couple guys who aren't smart enough to recognise that the valve isn't actually the problem, get them to go on the internet a create all kinds of hype and hysteria about how flawed the stock valves are and the end result is an awesome business making lots of money. And you know if the couple guys you got to create the hysteria were really gullible you wouldn't even have to pay them because they'd think you all were friends :rofl: Cheers, Paul. |
Originally Posted by '06 Quicksilver Z06
(Post 1586762703)
So you have one group of professionals from Manley saying one thing, and another from elsewhere saying another.
How do you know which one is right? Here I was thinking you have some ability in critical analysis and were able to make good judgements, you continue to prove me wrong so regularly it's embarrassing :rofl: Cheers, Paul. |
Originally Posted by '06 Quicksilver Z06
(Post 1586761397)
And you will also get the biggest fools who think that people can watch these stock valves fail time and again, and not take notice of it and advocate business as usual when it comes to this matter.
I'm hoping that there is no one at GM, or in here for that matter, like that though. Why are there oem heads straight from the supplier with machine issues which will lead to premature guide wear? Why are these valves dropping in some cars in a few thousand miles and others have clocked 100k plus? Oops.... The above facts negate Richards letter. Hes a smart guy and is a good head shop but in this case he over thought the issue and missed the mark. It happens to the best of them. Even the most brilliant minds of our time have had their theories proven wrong in time. |
Originally Posted by MTIRC6Z
(Post 1586763059)
SERIOUSLY...you have difficulty choosing between a long standing multi-million dollar company that ACTUALLY manufactures valves over a guy who slams some new guides and heavy-assed valves into a head to 'fix' it without know WHY the guides wore out in the first place :willy:
Here I was thinking you have some ability in critical analysis and were able to make good judgements, you continue to prove me wrong so regularly it's embarrassing :rofl: Cheers, Paul. |
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