Valve guide wear & UOA
- Thread starter MarkD
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Iron or brass, depending on the guides contruction but I think it will be harder to get back into the oil supply than say the cylinders or bearings wear metals.
Originally Posted By: MarkD
Can a UOA register wear metals caused by valve guides wearing? Specifically, the exhaust valve guide, which also has an oil seal.
Thanks
Mark
Hum... interesting question. Most of that wear would end up in the combustion chamber and go out the tail pipe. I guess if the valve guide had oil on it, and the wear metals got into that oil, it would flow down the valve and into the combustion chamber, and some, in theory, would get stuck to the cylinder walls and find it's way into the oil. But I would think this would be insignificant when it came to parts per million on a UOA normally generated by an operating engine. Lets say they are made of iron. How are you to know that the 25 ppm of iron you got on your UOA was supposed to be 23 ppm but the valve guide is wearing? Also, if you got a much larger number, say, an 85 ppm for iron, I highly doubt a valve guide would be your #1 culprit.
Edit: Oh, i just read your post again. Exhaust side? No, probably not. The wear would have to be on the valve stem when it came back up, and would have stay stuck on past the stem seal, wouldn't it?
Can a UOA register wear metals caused by valve guides wearing? Specifically, the exhaust valve guide, which also has an oil seal.
Thanks
Mark
Hum... interesting question. Most of that wear would end up in the combustion chamber and go out the tail pipe. I guess if the valve guide had oil on it, and the wear metals got into that oil, it would flow down the valve and into the combustion chamber, and some, in theory, would get stuck to the cylinder walls and find it's way into the oil. But I would think this would be insignificant when it came to parts per million on a UOA normally generated by an operating engine. Lets say they are made of iron. How are you to know that the 25 ppm of iron you got on your UOA was supposed to be 23 ppm but the valve guide is wearing? Also, if you got a much larger number, say, an 85 ppm for iron, I highly doubt a valve guide would be your #1 culprit.
Edit: Oh, i just read your post again. Exhaust side? No, probably not. The wear would have to be on the valve stem when it came back up, and would have stay stuck on past the stem seal, wouldn't it?
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Thanks. I was hoping that it could. The LS7/Z06 community has had some alarming exhaust valve failures (it's a two piece, sodium filled stainless valve) and in all circumstances the iron guides are excessively worn. Some that haven't experienced any failure have discovered during a head swap (port work) that even very low mileage examples are showing out of spec exhaust valve guide wear. The speculation is that wear is causing the valve head to "rock" back and forth and break.
Why it's happening no one yet knows. Some of these engines have been on the track, some have not.
I'm about to get my 2nd oil analysis results back (21k on the engine). The first one at 11k miles was perfect.
Why it's happening no one yet knows. Some of these engines have been on the track, some have not.
I'm about to get my 2nd oil analysis results back (21k on the engine). The first one at 11k miles was perfect.
Make sure you post your analysis!
Any date codes from the engines? I am curious is maybe there might be a link there.
Any ideas on the duty cycles of the engines that had failures? The sodium filled valves rely on higher rpm to allow sodium to move around.
Any ideas on the duty cycles of the engines that had failures? The sodium filled valves rely on higher rpm to allow sodium to move around.
OFF TOPIC
I would like to know why:
A) Valves are hollow
B) They are filled with sodium
Thanks.
I would like to know why:
A) Valves are hollow
B) They are filled with sodium
Thanks.
Originally Posted By: Chris Meutsch
OFF TOPIC
I would like to know why:
A) Valves are hollow
B) They are filled with sodium
Thanks.
A) To reduce weight, crucial to maintain control of the valves at high RPMs.
B) When the valves are running the Sodium liquifies and moves around inside the valve, think: cocktail shaker or lava lamp. The motion of the sodium move the heat from the valve face to the valve stem which is cooled by oil in the overhead.
OFF TOPIC
I would like to know why:
A) Valves are hollow
B) They are filled with sodium
Thanks.
A) To reduce weight, crucial to maintain control of the valves at high RPMs.
B) When the valves are running the Sodium liquifies and moves around inside the valve, think: cocktail shaker or lava lamp. The motion of the sodium move the heat from the valve face to the valve stem which is cooled by oil in the overhead.
Thanks. Thanks very much. Fascinating.
Roller rocker arms are a benefit to reduce valveguide wear, maybe the valve-seals are working too well. Some of the aftermarket heads valveguides are brass for better oil holding qualities. You could free up the seal some and trade oil consumption for durability. One piece stainless valves are less likely to break but you still do not want them rocking around. I know it is a chore to remove valvecovers but you could check the stem/guide play if you are very concerned.
Originally Posted By: 09_GXP
Any date codes from the engines? I am curious is maybe there might be a link there.
Any ideas on the duty cycles of the engines that had failures? The sodium filled valves rely on higher rpm to allow sodium to move around.
There hasn't been enough (or any, assuming GM hasn't looked into it) research to know this.
There have been low mileage LS7's with high guide wear. It might be a supplier QC issue with guides machined out of spec, but it's just a guess.
Any date codes from the engines? I am curious is maybe there might be a link there.
Any ideas on the duty cycles of the engines that had failures? The sodium filled valves rely on higher rpm to allow sodium to move around.
There hasn't been enough (or any, assuming GM hasn't looked into it) research to know this.
There have been low mileage LS7's with high guide wear. It might be a supplier QC issue with guides machined out of spec, but it's just a guess.
Originally Posted By: MarkD
There hasn't been enough (or any, assuming GM hasn't looked into it) research to know this.
There have been low mileage LS7's with high guide wear. It might be a supplier QC issue with guides machined out of spec, but it's just a guess.
I was curoius about the build dates since the valve guides are usually machined once they are pressed into the head. I was thinking that perhaps GMs tooling had worn out and was not machining the guides cleanly.
There hasn't been enough (or any, assuming GM hasn't looked into it) research to know this.
There have been low mileage LS7's with high guide wear. It might be a supplier QC issue with guides machined out of spec, but it's just a guess.
I was curoius about the build dates since the valve guides are usually machined once they are pressed into the head. I was thinking that perhaps GMs tooling had worn out and was not machining the guides cleanly.
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