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Old 11-27-2013, 08:09 PM   #1
Smokin04
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Default Here goes nothing: My take on the root cause and "the fix"...(long read)

I have discovered what I determined to be (in my opinion) the notorious valve issue. It is caused by 3 things. One of the three is more dominant than the other two. They're listed by order of severity.

1) Operating oil temps and weight. First we should be using a 0W-30 because 90% of engine wear happens on start-up. You want oil that thickens the least possible amount when cooling, but still offers protection (proper viscosity) in the needed pressure/temp range. Also, a lot of people don't realize that oil should be at least 10% (in general terms) hotter than the coolant to protect properly. When oil doesn't get above 212*(considered “normal operating temp”) it's not hot enough to boil away the water which it collects when not running, thus, it's considered contaminated or not protecting properly at a minimum. Problem is exacerbated further in the ZO6 because not only does oil not reach 10% hotter, it doesn't even reach 200* in most street applications. This can be why we're seeing failures of stock (unmodded or lightly modded) street cars. It's well documented that oil needs to reach 200+ to even work properly (or achieve operating temp). The track guys (environment where the ZO6 was designed to survive in) often see (average) normal oil temps of 250-260 with coolant in the 220 range. This is the "sweet spot" for proper engine protection and function as designed by GM. But when those track cars operate on the street as well...that's where their excessive engine wear is coming to fruition...much like the rest of us. This has to do with the materials being utilized (IE Sodium filled valves…more on that later).

2) Poor exhaust rocker arm side loading. Now I actually measured the deflection on my car when the rockers were swapped for Yella Terra's. How does .382 grab you? (This was the extreme case, as there was typically between .250 - .300 on the others) That’s almost half an inch of deflection. This was measured on 4 separate exhaust valve with my dial indicator. It was so extreme; you could see it with the naked eye. Notably, there was virtually zero deflection on the intake side. This deflection will have the effect of unwanted pre-load or “side load” with every opening of the valve. It makes sense to me that the severity of the deflection would vary from engine to engine. This can be why some valves fail at 5K miles and why some last longer. Combine this with oil not being able to protect the way it should...the proverbial plot thickens. Some might say this is more severe than the oil temp…and you could argue a case to that point. I think that these are both serious issues, but this issue would be less of an issue if the oil could protect properly.

3) Sodium-filled valves.
Now this is where it gets tricky. Sodium valves work VERY well. Once they reach 206* the sodium liquefies and begins transferring heat to the heads through the guides. Normally, this is a good thing. In our case however, the sodium actually cools to a point that it keeps oil temps at bay (hindering the oil temps reaching normal operating temp). On the track this is a non-issue and where the valve was intended for use (also why GM used them IMO). Yes the "weight issue" can be brought up here, but not really because GM could've used titanium (or hollow stainless) if they were worried about weight vs. heat transfer. So GM using the sodiums makes the problem worse for the street guys. Ideally, you could have a solid (or hollow stemmed) valve head for the street, and the sodium equipped for the track days. Obviously, guys aren’t going to swap heads every time they want to run, so GM elected to go for the big guns and protect the track guys. Fair enough. I don’t think GM counted on the oil temps being so low. But one can only speculate on GM’s decision for using this valve at the corporate level. All we can do is protect our investments with research and appropriate counter-measures.

Combine these 3 issues, oil not protecting with horrible pre-load, and thin walled sodium-filled valves, you have found a recipe for failure. The sodium chamber can develop frictional "hot-spots" from the excessive side load that will eventually fatigue just below the sodium chamber (its thinnest/most sensitive point) and eventually break causing the head of the valve to break off. This excessive wear occurs with every mile but really only has to occur once or twice to start the proverbial "snowball" rolling down-hill. This wear is occurring at the factory level, and only gets worse as the miles add. Once started...there is no repair unless you replace the guides (or heads) such as GM is doing. Without regulating the oil temps, and fixing the rocker pre-load...you could change heads a dozen times and the problem will likely still occur. Even in my case, with proper oil temp control, and corrected geometry, the damage is done and I too will need new guides/heads.

The debate about stainless valves versus sodium-filled valves truly comes down to preference. There are literally thousands if not tens of thousands of successful cases of stainless valves being used in intake and exhaust locations. Stainless valves in performance applications is hardly a news flash and their reputation as reliable valves in performance applications can NOT be debated. But, this is also why I say it’s a matter of preference. Sure, sodium-filled valves can be lighter; but they’re generally utilized for their better heat transferring capability in dedicated racing engines. They were not designed with 200K miles in mind. Also worth noting; with continuously developing tech in metal alloys you’d be surprised at how insignificant the weight variance between the two really is. As a general rule, you want the valve train as rigid and light as possible. Personally, I agree. But, not at the sacrifice of longevity. Even if you control oil temps and side load, a sodium-filled valve is still weaker structurally, than a solid stainless valve. So I will vocalize my opinion and say that based on the track record of the sodiums, a solid valve is the better choice on a street motor.

Valve guide material choices also are a preference in my opinion. I personally have run manganese bronze guides in a street car for well north of 100K miles. This was a street/strip application…about 90% street, 10% track. Is bronze a “better” choice than powdered metal? Personally, I think the difference is negligible on either street or track applications. All have their merits and preferred applications, but I doubt any recordable/measurable difference exists between the guide materials in a street application.

The “fix.”
Based on information publicly available, compilation of data from this board, and other conducted research…I believe that fixing the oil temp issue is the FIRST step in the “fix.” Blocking off your oil cooler with something that denies airflow will allow your oil to reach “normal operating temp” and protect properly. Once that is accomplished, address the rocker geometry issue. Either run an aftermarket setup, or find a way to make sure your rockers have NO deflection or side-load. A centered wipe pattern is NOT enough. You have to ensure there is no deflection and proper geometry. This ensures that you’re not chewing up your freshly installed valve guides. Is this possible to do with stock rockers? I honestly don’t know. I know I have not tried because it was easier (on the wallet too) to just go with aftermarket shaft style. Starting over with fresh (read: unworn) guides is necessary. You can use whatever guides you choose. You can replace them in the stock castings, or use aftermarket heads. But if you haven’t addressed the oil temp issue, your new heads/guides may already be being worn. Once these issues are addressed, you can elect to re-use the stock valves, or replace them with stainless variants. Personally, if it’s longevity you’re after, I would choose the solid stainless valves. After you have addressed these issues, in my opinion you’re no longer in danger of engine damage caused by exhaust valve failure.

Sorry this was long winded, but this is my input to the string of failures. There are many inputs from numerous people out there as to their interpretations of what the cause and “fix” is for these engines. This thread is not intended to de-bunk or disagree with any previously listed hypotheses from other members. These are just my thoughts based on independent research I have conducted for the purpose of self-enlightenment. I am an analyst by profession, and a mechanic by passion. I am only trying to help the community for which I have developed a fondness. I think the ZO6 is a supercar, and I absolutely love mine. I know I’m not alone in this passion, and these are sensitive times for us…especially when money gets involved. If you feel what I listed is not an accurate portrayal of the real issue; I encourage you help the community and your own interests by conducting your own data collection and research efforts, and post for the community to see. Hopefully, this has helped someone.

Last edited by Smokin04; 11-28-2013 at 10:11 AM. Reason: spelling
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Old 11-27-2013, 08:13 PM   #2
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Interesting post and thanx for your opinions. I've run 0-40w for sometime and hopefully this makes some difference.
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Old 11-27-2013, 08:16 PM   #3
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Agreed that oil temp probably plays a huge roll. They take FOREVER to heat up to proper oil temp. For 95% of the people I bet a great mod would be to do like base vettes and just have no oil cooler. Run the bypass part. You only need an oil cooler if you are beating on it at the track. For those people they can keep one and uncover it when at the racetrack.

Another option is a air/water like the later z06/zr1. Dewitts has a nice setup. My oil temps comp up much faster with the dewitts oil cooler.
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Old 11-27-2013, 08:26 PM   #4
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Excellent post, great read and makes a lot if sense.

I'm a firm believer that you can't volunteer to count ballots in an election that you're running in, win the election, and then wonder why not everybody is on board with it.

You can't officiate over a horse race that you have horses running in, and when nary another horse even "shows", let alone wins or places, wonder why that would raise some eyebrows.

What I mean to say here, is that independent testing, with no vendor within 100 yards of the testing, done on a setup such as you describe, real world and with the oil you describe.

I'd bet the outcome would be interesting, to say the least.
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Old 11-27-2013, 08:41 PM   #5
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Quote:
Originally Posted by Unreal View Post
Agreed that oil temp probably plays a huge roll. They take FOREVER to heat up to proper oil temp. For 95% of the people I bet a great mod would be to do like base vettes and just have no oil cooler. Run the bypass part. You only need an oil cooler if you are beating on it at the track. For those people they can keep one and uncover it when at the racetrack.

Another option is a air/water like the later z06/zr1. Dewitts has a nice setup. My oil temps comp up much faster with the dewitts oil cooler.
Or one could use an oil thermostat, or thermal blanket on the oil reservoir to try and keep the oil warm before start up and during operation to get temps up quickly.
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Old 11-27-2013, 08:57 PM   #6
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Interesting and thoughtful post. I have been babying the car around town as those trips are so short that the oil temp never comes up. So I keep the rpm below 3000 rpm until I get to 190 F or so. That actually means I might as well drive a Yugo or Toyota for those short trips.

Based on your post I will buy one of Jason Swindle's adjustable oil cooler blankets right now. He runs his fully closed in the LA winters (not much winter there) and half open in the summer. It certainly can't hurt and could allow me to have more fun with the car on short trips.
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Old 11-27-2013, 09:03 PM   #7
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Interesting that you mention warming up and oil temps, and the sodium valve doing too good of a job cooling.

Here is a link to a patent that discusses higher melting point alloys than sodium in hollow exhaust valves to avoid supercooling of the valve head.

US Patent 5769037 (1998) assigned to Fuji Oozx Inc.

http://www.google.com.mx/patents/US5769037

From the link:

Quote:
Metal Na is solid at room temperature and melted at operating temperature of the valve element. But the melting point thereof is relatively low, such as about 98 during warm-up operation of the engine or low speed operation right after running, and the valve head may be subjected to supercooling by heat exchange of metal Na. So self-cleaning action fails, so that combustion product which is contained in an exhaust gas or lubricating oil which drops owing to oil-down is adhered and deposited on the valve head.
SUMMARY OF THE INVENTION

To overcome the disadvantages, it is an object to provide a hollow valve in an internal combustion engine, wherein cooling medium other than metal Na is enclosed in a cavity, thereby facilitating manufacture and preventing a valve head from being subjected to supercooling.
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Old 11-27-2013, 09:05 PM   #8
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I think you are on to something with your post, especially the oil temps. But that does lead me to ask a question. Since, as you say, 90% of wear occurs at cold startup, how does that justify using a 20 weight at normal operating temps. I think a 0W-40 would be better than a 0W-20. At cold start, the viscosity would be the same, at full temp, the 40 weight will likely provide higher pressures, and a better dynamic oil wedge formation at hi rpm. Thoughts?
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Old 11-27-2013, 09:15 PM   #9
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I've always understood the oil boiling out the water/contaminates thing, but I don't think the oil weight and temps play much of a part here.

I cant remember a car that had an oil temp gauge that ever reached 200 degrees in normal driving. That always made me wonder if the oil was getting hot enough. My oil cooled 964 was never near 200 unless I was stuck in traffic. At highway speeds it was always well under 200 degrees.

As far as flow/protection once the oil reaches 100 degrees, it flows as well as it does at 200. The oil pressure in my Z06 is always high when cold, and as the oil warms it drops, as it should. Once the temps get to 100, the pressure levels out. 5K rpm or idle with the oil at 100 degrees, gives the same oil pressure with the oil at 180 degrees. Get near 5K rpm with the oil under 100 degrees and the oil pressure needle is easily pegged. I use Amsoil 0-30 if that matters.

I've seen many Blackstone Analysis reports here and none have ever reported anything contaminating the oil, which could be caused by the oil running too cold. Ive seen contaminated oil before when its changed, and no here has ever said their oil was milky or odd looking during an oil change.

I still think this is all well intended guess work among the collective in this forum. The only source with a large enough sample, and data to actually back up any hypothesis is GM, and they aren't sharing what they know.
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Old 11-27-2013, 09:40 PM   #10
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Quote:
Originally Posted by '06 Quicksilver Z06 View Post
[...] I'd bet the outcome would be interesting, to say the least.
Indeed... with 0W20 oil the engine would probably seize within 5 hours of dyno time. Of course, since it would probably be a vendor's dyno it wouldn't count, right?
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Old 11-27-2013, 09:41 PM   #11
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Quote:
Originally Posted by ByByBMW View Post
I think you are on to something with your post, especially the oil temps. But that does lead me to ask a question. Since, as you say, 90% of wear occurs at cold startup, how does that justify using a 20 weight at normal operating temps. I think a 0W-40 would be better than a 0W-20. At cold start, the viscosity would be the same, at full temp, the 40 weight will likely provide higher pressures, and a better dynamic oil wedge formation at hi rpm. Thoughts?
The viscosity of 20wt vs 40wt at cold temp is different. Read here:
http://www.bobistheoilguy.com/motor-oil-102/

Quote:
Originally Posted by birdflu View Post
I've always understood the oil boiling out the water/contaminates thing, but I don't think the oil weight and temps play much of a part here.

I cant remember a car that had an oil temp gauge that ever reached 200 degrees in normal driving. That always made me wonder if the oil was getting hot enough. My oil cooled 964 was never near 200 unless I was stuck in traffic. At highway speeds it was always well under 200 degrees.
Understood...but perhaps the engines you're referring to (while not reaching normal temp) were not paired with the same poor rocker geometry, and thin walled valves as the LS7. So while guide wear would be present in those engines, so would the majority of wear on all the surfaces, bearings or otherwise which over time would appear as normal wear. But that wear would be not as severe as the guide wear on the LS7. The LS7 probably has significant wear on the bearing surfaces as well...but because the valves fail so much sooner than the bearings, perhaps nobody thinks to check on them as well.
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Old 11-27-2013, 09:42 PM   #12
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Quote:
Originally Posted by Mark200X View Post
Indeed... with 0W20 oil the engine would probably seize within 5 hours of dyno time. Of course, since it would probably be a vendor's dyno it wouldn't count, right?
Why would you think the engine would seize with 0w-20 Mark?
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Old 11-27-2013, 09:45 PM   #13
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interesting..

what are you guys waiting for hte oil temp to get up to before going WOT.. most say 135+.. i drove my car around for quite a while today and it took a while to get up to 189 and stayed there for quite some time..
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Old 11-27-2013, 09:50 PM   #14
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Originally Posted by TT32VGT View Post
interesting..

what are you guys waiting for hte oil temp to get up to before going WOT.. most say 135+.. i drove my car around for quite a while today and it took a while to get up to 189 and stayed there for quite some time..
I always waited until 150, but after this period of collecting data...I won't go WOT until 200+.
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Old 11-27-2013, 09:56 PM   #15
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The 2014 5.3 trucks are specifying 0W-20 weight oil. Might be something to consider.

Good info Smokin. I wonder too if our guide seals are doing too good a job. Has anybody removed the top valve stem seal spring. Might let more lube down into the guide. In the old days umbrella seals were used which allowed more oil to the guides.
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Old 11-27-2013, 09:57 PM   #16
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Quote:
Originally Posted by Smokin04 View Post

Understood...but perhaps the engines you're referring to (while not reaching normal temp) were not paired with the same poor rocker geometry
I think I'm accurate in stating 99% of the cars on the road today never reach oils temps that fall into what you are defining as "normal operation temps". I think modern oils(dino and synthetic) perform wonderfully. I know my Z06 has never had the oil in what I also consider "normal operating temps".
I think you are correct when you mention geometry. Every LS7 isn't exploding. Some are being tested, and show no signs of valve guide wear, all the while running the average low oil temps. I think this is a mechanical thing, some heads were put out with the wrong geometry, and others with the correct geometry.
I think if you have a bad head, its gonna fall apart no matter what oil is used at what temps, on the track, or pulling out of your driveway. There is nothing consistent about the conditions of the reports of those engines that have failed. How do any of us know if we have a good head or not? Thats the million dollar question.
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Old 11-27-2013, 10:12 PM   #17
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When I put in my new 2013 LS7 motor, one thing I liked was the new style oil cooler GM uses on the ZR1s. Before the car would take me the whole drive to work to get to 150F (about 20 mins). Now, it takes half that and is in the 200-215F range for MOST of the drive. I do use 5W30 oil, I will be switching to 0W40 at next change. I dont know about 0W20, Id like to see some in here first put serious miles with it before I switch..

What did you find the over the tip weight of the Yella Terras to be? I have heard they range in the 20g area whereas stock is around 8-9g.
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Old 11-27-2013, 10:13 PM   #18
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Quote:
Originally Posted by birdflu View Post
How do any of us know if we have a good head or not? Thats the million dollar question.
I do agree with your whole post birdflu. As much as I hate to admit it...modern engines that don't see oil reach 200* I would surmise that it's a trade-off that the manufacture is okay with.

The question above is so true. Easily solved with a simple test. Unbolt your valve cover...doesn't matter which. Hook up a dial indicator to the side of your exhaust rocker. Unbolt it and measure (while making sure the cam is on the base circle) via the dial indicator the movement. I would say anything over .050 of movement would indicate faulty geometry and need to be addressed. Of course the .050 measurement is subjective...but I feel it's a good starting point.
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Old 11-27-2013, 10:19 PM   #19
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Quote:
Originally Posted by Smokin04 View Post
The viscosity of 20wt vs 40wt at cold temp is different. Read here:
http://www.bobistheoilguy.com/motor-oil-102/
I'm pretty dense tonight I guess. Nothing in your reference tells me why either 0W oil should be different viscosity at 75F .
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Old 11-27-2013, 10:21 PM   #20
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Quote:
Originally Posted by '06 Quicksilver Z06 View Post
Excellent post, great read and makes a lot if sense.

I'm a firm believer that you can't volunteer to count ballots in an election that you're running in, win the election, and then wonder why not everybody is on board with it.

You can't officiate over a horse race that you have horses running in, and when nary another horse even "shows", let alone wins or places, wonder why that would raise some eyebrows.

What I mean to say here, is that independent testing, with no vendor within 100 yards of the testing, done on a setup such as you describe, real world and with the oil you describe.

I'd bet the outcome would be interesting, to say the least.
Don't agree with this and I think its a bad analogy. Just being honest. Vendor does not equal corrupt. Id love to see independent also but I think a lot of the testing we get here (free of cost) is indeed, accurate. I can smell a rat just as good as anyone but lets be honest with ourselves, did you honestly think, and Ill use Katech as an example, that a 98g valve wouldn't have any bounce and would be stable at 7,000 RPM? The results made sense. If they showed less bounce than a stock setup, I'm assuming you'd have backed the results.
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