[Z06] Bronze Valve Guide Inspection
05-13-2013, 12:31 PM
#1
Racer
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Bronze Valve Guide Inspection
Just wanted to share my findings with the community, i wanted to title the thread differently so there wasn't yet ANOTHER guide thread, but figured i should be straight forward haha.
So the background on the car is 2006 Z06, pulled the heads, terrible guide wear. Had West coast go through them, after a good deal of research decided to go the solid stemmed route. Put a relatively mild cam in with .660" intake and .663" exhaust, patriot dual extreme springs and 25,000 miles on this setup. I drive a good deal of mixed habits, weekend cruises, commuting, and rip on it every chance i get. So here are the results, i will say as a whole i am pretty pleased. Not elated but we will touch upon that and a couple other things later.
[IMG]
Valve clearances | Flickr - Photo Sharing! [/IMG]
I did not list the intake valves because they were all extremely tight, with less than a couple thou of wiggle.
I called WCCH to ask them about my findings and i also spoke to Brian Tooley (great guy, super nice and seemed very knowledgeable) to pick his brain when i ordered my new springs.
West coast said they weren't surprised by these readings, they said my build was one that was of earlier ones and they were running the guides a touch larger (.0015-.0017) than current ones for a couple reasons. 1, they needed to in order to get the guide straight and then final reamed and 2 the guides they get now have a thicker wall to allow them to get it straight and then cut the final size.
Also just my personal opinion, i have a feeling they are learning as well with all the head work they are doing and have opted just to tighten them up because of all the daily drivers and cruisers they are doing. When building a race motor you run them a touch looser to account for thermal expansion and to avoid sticking the valve.
Brian stated he wasn't surprised at all, and that he prefers to run the iron guides because the bronze WILL wear. He had suggested a shop he deals with that specializes in this because of the difficulty associated with machining them. If i keep the car long enough to need them done again i will definitely be going this route, with solid stemmed units.
AAaannnddd there had been some people stating that there hadn't been a clear reason specified as to why the solid stemmed route posed any real solution over the sodium filled. So my curiosity got the best of me. Other than the research i had done showing failures in airplanes, cars, boats running these little technically savvy but problematic valves i wanted some more hard proof they could be fragile. I modeled up the valve to the best of my ability and did some FEA with the closed pressures of the springs i'm running.
Hollow stemmed model:
[IMG] valve section | Flickr - Photo Sharing![/IMG]
Hollow stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
[IMG] hollow stem stress | Flickr - Photo Sharing![/IMG]
Solid stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
[IMG] Solid valve stress | Flickr - Photo Sharing![/IMG]
Please keep in mind that the distortions shown are for illustrative purposes. Solidworks extends them so you get a visual feel for how th part will distort. the actual displacement is only in the neighborhood of .005" but the stress is the same.
Also, the FEA was not done under a heated condition. And it does not take into account instantaneous loading, which this is clearly a case of impact loading making it an even more harsh environment. As you guys can see a heavy spring would not suit these. Likely why GM chose a spring with only 100lbs at closed. I didnt have time to do the FEA on the lower pressure but i'm sure i could do it in the next couple days. anyway lets try and keep it civil.
So the background on the car is 2006 Z06, pulled the heads, terrible guide wear. Had West coast go through them, after a good deal of research decided to go the solid stemmed route. Put a relatively mild cam in with .660" intake and .663" exhaust, patriot dual extreme springs and 25,000 miles on this setup. I drive a good deal of mixed habits, weekend cruises, commuting, and rip on it every chance i get. So here are the results, i will say as a whole i am pretty pleased. Not elated but we will touch upon that and a couple other things later.
[IMG]
Valve clearances | Flickr - Photo Sharing! [/IMG]I did not list the intake valves because they were all extremely tight, with less than a couple thou of wiggle.
I called WCCH to ask them about my findings and i also spoke to Brian Tooley (great guy, super nice and seemed very knowledgeable) to pick his brain when i ordered my new springs.
West coast said they weren't surprised by these readings, they said my build was one that was of earlier ones and they were running the guides a touch larger (.0015-.0017) than current ones for a couple reasons. 1, they needed to in order to get the guide straight and then final reamed and 2 the guides they get now have a thicker wall to allow them to get it straight and then cut the final size.
Also just my personal opinion, i have a feeling they are learning as well with all the head work they are doing and have opted just to tighten them up because of all the daily drivers and cruisers they are doing. When building a race motor you run them a touch looser to account for thermal expansion and to avoid sticking the valve.
Brian stated he wasn't surprised at all, and that he prefers to run the iron guides because the bronze WILL wear. He had suggested a shop he deals with that specializes in this because of the difficulty associated with machining them. If i keep the car long enough to need them done again i will definitely be going this route, with solid stemmed units.
AAaannnddd there had been some people stating that there hadn't been a clear reason specified as to why the solid stemmed route posed any real solution over the sodium filled. So my curiosity got the best of me. Other than the research i had done showing failures in airplanes, cars, boats running these little technically savvy but problematic valves i wanted some more hard proof they could be fragile. I modeled up the valve to the best of my ability and did some FEA with the closed pressures of the springs i'm running.
Hollow stemmed model:
[IMG]
valve section | Flickr - Photo Sharing![/IMG]Hollow stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
[IMG]
hollow stem stress | Flickr - Photo Sharing![/IMG]Solid stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
[IMG]
Solid valve stress | Flickr - Photo Sharing![/IMG]Please keep in mind that the distortions shown are for illustrative purposes. Solidworks extends them so you get a visual feel for how th part will distort. the actual displacement is only in the neighborhood of .005" but the stress is the same.
Also, the FEA was not done under a heated condition. And it does not take into account instantaneous loading, which this is clearly a case of impact loading making it an even more harsh environment. As you guys can see a heavy spring would not suit these. Likely why GM chose a spring with only 100lbs at closed. I didnt have time to do the FEA on the lower pressure but i'm sure i could do it in the next couple days. anyway lets try and keep it civil.
Last edited by 240sx2jz; 05-13-2013 at 02:53 PM.
05-13-2013, 02:18 PM
#3
Burning Brakes
Just wanted to share my findings with the community, i wanted to title the thread differently so there wasn't yet ANOTHER guide thread, but figured i should be straight forward haha.
So the background on the car is 2006 Z06, pulled the heads, terrible guide wear. Had West coast go through them, after a good deal of research decided to go the solid stemmed route. Put a relatively mild cam in with .660" intake and .663" exhaust, patriot dual extreme springs and 25,000 miles on this setup. I drive a good deal of mixed habits, weekend cruises, commuting, and rip on it every chance i get. So here are the results, i will say as a whole i am pretty pleased. Not elated but we will touch upon that and a couple other things later.
[IMG]Valve clearances | Flickr - Photo Sharing! Valve clearances | Flickr - Photo Sharing! by DSeddon1, on Flickr[/IMG]
I did not list the intake valves because they were all extremely tight, with less than a couple thou of wiggle.
I called WCCH to ask them about my findings and i also spoke to Brian Tooley (great guy, super nice and seemed very knowledgeable) to pick his brain when i ordered my new springs.
West coast said they weren't surprised by these readings, they said my build was one that was of earlier ones and they were running the guides a touch larger (.0015-.0017) than current ones for a couple reasons. 1, they needed to in order to get the guide straight and then final reamed and 2 the guides they get now have a thicker wall to allow them to get it straight and then cut the final size.
Also just my personal opinion, i have a feeling they are learning as well with all the head work they are doing and have opted just to tighten them up because of all the daily drivers and cruisers they are doing. When building a race motor you run them a touch looser to account for thermal expansion and to avoid sticking the valve.
Brian stated he wasn't surprised at all, and that he prefers to run the iron guides because the bronze WILL wear. He had suggested a shop he deals with that specializes in this because of the difficulty associated with machining them. If i keep the car long enough to need them done again i will definitely be going this route, with solid stemmed units.
AAaannnddd there had been some people stating that there hadn't been a clear reason specified as to why the solid stemmed route posed any real solution over the sodium filled. So my curiosity got the best of me. Other than the research i had done showing failures in airplanes, cars, boats running these little technically savvy but problematic valves i wanted some more hard proof they could be fragile. I modeled up the valve to the best of my ability and did some FEA with the closed pressures of the springs i'm running.
Hollow stemmed model:
[IMG]valve section | Flickr - Photo Sharing! valve section | Flickr - Photo Sharing! by DSeddon1, on Flickr[/IMG]
Hollow stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
hollow stem stress | Flickr - Photo Sharing!
hollow stem stress | Flickr - Photo Sharing! by DSeddon1, on Flickr
Solid stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
Solid valve stress | Flickr - Photo Sharing!
Solid valve stress | Flickr - Photo Sharing! by DSeddon1, on Flickr
Please keep in mind that the distortions shown are for illustrative purposes. Solidworks extends them so you get a visual feel for how th part will distort. the actual displacement is only in the neighborhood of .005" but the stress is the same.
Also, the FEA was not done under a heated condition. And it does not take into account instantaneous loading, which this is clearly a case of impact loading making it an even more harsh environment. As you guys can see a heavy spring would not suit these. Likely why GM chose a spring with only 100lbs at closed. I didnt have time to do the FEA on the lower pressure but i'm sure i could do it in the next couple days. anyway lets try and keep it civil.
So the background on the car is 2006 Z06, pulled the heads, terrible guide wear. Had West coast go through them, after a good deal of research decided to go the solid stemmed route. Put a relatively mild cam in with .660" intake and .663" exhaust, patriot dual extreme springs and 25,000 miles on this setup. I drive a good deal of mixed habits, weekend cruises, commuting, and rip on it every chance i get. So here are the results, i will say as a whole i am pretty pleased. Not elated but we will touch upon that and a couple other things later.
[IMG]Valve clearances | Flickr - Photo Sharing! Valve clearances | Flickr - Photo Sharing! by DSeddon1, on Flickr[/IMG]
I did not list the intake valves because they were all extremely tight, with less than a couple thou of wiggle.
I called WCCH to ask them about my findings and i also spoke to Brian Tooley (great guy, super nice and seemed very knowledgeable) to pick his brain when i ordered my new springs.
West coast said they weren't surprised by these readings, they said my build was one that was of earlier ones and they were running the guides a touch larger (.0015-.0017) than current ones for a couple reasons. 1, they needed to in order to get the guide straight and then final reamed and 2 the guides they get now have a thicker wall to allow them to get it straight and then cut the final size.
Also just my personal opinion, i have a feeling they are learning as well with all the head work they are doing and have opted just to tighten them up because of all the daily drivers and cruisers they are doing. When building a race motor you run them a touch looser to account for thermal expansion and to avoid sticking the valve.
Brian stated he wasn't surprised at all, and that he prefers to run the iron guides because the bronze WILL wear. He had suggested a shop he deals with that specializes in this because of the difficulty associated with machining them. If i keep the car long enough to need them done again i will definitely be going this route, with solid stemmed units.
AAaannnddd there had been some people stating that there hadn't been a clear reason specified as to why the solid stemmed route posed any real solution over the sodium filled. So my curiosity got the best of me. Other than the research i had done showing failures in airplanes, cars, boats running these little technically savvy but problematic valves i wanted some more hard proof they could be fragile. I modeled up the valve to the best of my ability and did some FEA with the closed pressures of the springs i'm running.
Hollow stemmed model:
[IMG]valve section | Flickr - Photo Sharing! valve section | Flickr - Photo Sharing! by DSeddon1, on Flickr[/IMG]
Hollow stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
hollow stem stress | Flickr - Photo Sharing!
hollow stem stress | Flickr - Photo Sharing! by DSeddon1, on Flickr
Solid stemmed FEA with 150lbs landing on the seat at a slight angle representing guide wear:
Solid valve stress | Flickr - Photo Sharing!
Solid valve stress | Flickr - Photo Sharing! by DSeddon1, on Flickr
Please keep in mind that the distortions shown are for illustrative purposes. Solidworks extends them so you get a visual feel for how th part will distort. the actual displacement is only in the neighborhood of .005" but the stress is the same.
Also, the FEA was not done under a heated condition. And it does not take into account instantaneous loading, which this is clearly a case of impact loading making it an even more harsh environment. As you guys can see a heavy spring would not suit these. Likely why GM chose a spring with only 100lbs at closed. I didnt have time to do the FEA on the lower pressure but i'm sure i could do it in the next couple days. anyway lets try and keep it civil.
1. Hollow valve yield strength is around 90 k psi and the stress levels where the valves seem to be breaking is around 30% of yield. (GOOD MARGIN)
2. Hollow with 150 psi spring has same yield with about 50% margin also in the region where the valves seem to break (Not healthy amount of margin)
3. The Solid with 150 psi spring also has same yield but with around 30% of yield margin (GOOD MARGIN)
The Hollow valve with 100 psi spring stress level margin is equivalent to the solid with 150 psi spring..
Now the 64 $ question is how will the levels and margins vary with thermal loading?
05-13-2013, 02:26 PM
#4
Drifting
I'm still trying to figure out the first couple charts you posted. Is the left column the actual clearance observed from a wiggle measured with dial indicator? Or are you actually measuring this with bore calipers for the guide and regular calipers for the valve?
From what I understand, if you doing with wiggle/dial indicator you would divide that measurement by 2 to get close to the measurement you would derive from a bore caliper.
What is TIR? Is FEA finite element analysis?
From what I understand, if you doing with wiggle/dial indicator you would divide that measurement by 2 to get close to the measurement you would derive from a bore caliper.
What is TIR? Is FEA finite element analysis?
05-13-2013, 02:40 PM
#5
Burning Brakes
I'm still trying to figure out the first couple charts you posted. Is the left column the actual clearance observed from a wiggle measured with dial indicator? Or are you actually measuring this with bore calipers for the guide and regular calipers for the valve?
From what I understand, if you doing with wiggle/dial indicator you would divide that measurement by 2 to get close to the measurement you would derive from a bore caliper.
What is TIR? Is FEA finite element analysis?
From what I understand, if you doing with wiggle/dial indicator you would divide that measurement by 2 to get close to the measurement you would derive from a bore caliper.
What is TIR? Is FEA finite element analysis?
05-13-2013, 02:40 PM
#6
Drifting
His point is:
Under the same steady state, non-heated conditions, the hollow valve will experience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
Under the same steady state, non-heated conditions, the hollow valve will experience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
05-13-2013, 02:41 PM
#7
Melting Slicks
His point is:
Under the same steady state, non-heated conditions, the hollow valve will experience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
Under the same steady state, non-heated conditions, the hollow valve will experience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
cha cha cha....
05-13-2013, 02:48 PM
#8
Drifting
05-13-2013, 03:00 PM
#10
Melting Slicks
That's true, I don't think we have had a proven root cause yet. The SS valve replacement adds strength but at the expense of weight. No long term tests have been done as to its effect. I was hoping this thread would at least rule out guide wear by moving to bronze.
We simply know where its breaking, not whats causing it to get to the breaking point.
05-13-2013, 03:01 PM
#11
Burning Brakes
His point is:
Under the same steady state, non-heated conditions, the hollow valve willexperience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
Under the same steady state, non-heated conditions, the hollow valve willexperience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
05-13-2013, 03:01 PM
#12
Racer
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I'm still trying to figure out the first couple charts you posted. Is the left column the actual clearance observed from a wiggle measured with dial indicator? Or are you actually measuring this with bore calipers for the guide and regular calipers for the valve?
From what I understand, if you doing with wiggle/dial indicator you would divide that measurement by 2 to get close to the measurement you would derive from a bore caliper.
What is TIR? Is FEA finite element analysis?
From what I understand, if you doing with wiggle/dial indicator you would divide that measurement by 2 to get close to the measurement you would derive from a bore caliper.
What is TIR? Is FEA finite element analysis?
And if these guides were reamed to a clearance of .0015 that would mean the max wear has been 0.0018 or just about 2/3rds of a piece of paper.....
05-13-2013, 03:13 PM
#13
Burning Brakes
Can you input temperatures in the model?
05-13-2013, 03:25 PM
#14
Racer
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His point is:
Under the same steady state, non-heated conditions, the hollow valve will experience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
Under the same steady state, non-heated conditions, the hollow valve will experience 92k psi of stress and the solid valve will experience 52k.
Values are probably wrong considering thermal expansion during operation, lubrication, instantaneous forces as he said in his post, but the purpose of the exercise is to highlight the structural weakness of the hollow valve.
Also, he says bronze guides bad iron guides good.
But, it does make you wonder if the stem gets tweaked at the hightest stress region it could stick and then get whacked by the piston. which is what i tentatively think may be happening for the failures. After seeing that stressed area it seemed possible that the valve could stick and then get smoked.
05-13-2013, 03:30 PM
#15
I spoke with Richard a few months ago, back in September 2012, and he told me that they now send these heads out with guide to stem clearances of .0012-.0015".
If the starting tolerances were .0015-.0017", then the condition of and wear on these guides is not bad at all.
Also, your stock intake valves were re used and you say that the clearances on the intake side appear to be ok.
So I guess that Ti/Mo coated intake valves would have not made much difference here.
But all of this is interesting considering that GM's Production values for the stock guide clearances runs from .001"-.0026" on the exhaust side, leaving as little as .0011" on the exhaust side to go before one would hit the service limit.
Also, on a side note, GM lists .0037" as the service limit for the stock guide and stock valve setup.
Does anyone know how they arrived at this figure for their service limit?
Last edited by '06 Quicksilver Z06; 05-13-2013 at 07:32 PM.
05-13-2013, 03:47 PM
#16
Racer
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05-13-2013, 03:57 PM
#17
Drifting
Now take a look at existing failures:
Do the breaks agree with your findings?
Confirm/debunk this so we can move on to root causes.
05-13-2013, 04:02 PM
#18
Melting Slicks
There's no unifying theoretical formula when it comes to FEA and fatigue analysis. We're just pointing out where it is most likely to break.
Now take a look at existing failures:
Do the breaks agree with your findings?
Confirm/debunk this so we can move on to root causes.
Now take a look at existing failures:
Do the breaks agree with your findings?
Confirm/debunk this so we can move on to root causes.
05-13-2013, 04:40 PM
#19
Burning Brakes
There's no unifying theoretical formula when it comes to FEA and fatigue analysis. We're just pointing out where it is most likely to break.
Now take a look at existing failures:
Do the breaks agree with your findings?Confirm/debunk this so we can move on to root causes.
Now take a look at existing failures:
Do the breaks agree with your findings?Confirm/debunk this so we can move on to root causes.
