[Z06] Motor let go
11-06-2011, 09:11 AM
#681
Safety Car
11-06-2011, 10:01 AM
#682
Le Mans Master
11-06-2011, 10:03 AM
#683
Le Mans Master
I was one of the four standing there when the discussion was taking place. Some of the technicians were aware of the discussions on this forum regarding the engines, and were quiet amused as some of the claims. If Jim wants to tell you he will. But believe me, some will not like it.
That's wonderful that they got a laugh out of this, but this isn't a trivial deal to the owners of these cars.
And why are you using a pic of "for0tmypen"'s car in your avatar?
Last edited by AirBusPilot; 11-06-2011 at 10:06 AM.
11-06-2011, 10:41 AM
#684
Bingo.Easiest thing in the world for them to do.
I'm glad that it's amusing for them. But you are absolutely right, it's not trivial for the several people in here who have been hit by it, nor the people who don't know if they will be next......
I never personally discounted a bad batch scenario either, and I've NEVER bashed GM or the engineers. If this is indeed a bad batch scenario, it still does me no good if I don't know if I was a recipient of the bad batch or not, especially now that my warranty is expired.
I never personally discounted a bad batch scenario either, and I've NEVER bashed GM or the engineers. If this is indeed a bad batch scenario, it still does me no good if I don't know if I was a recipient of the bad batch or not, especially now that my warranty is expired.
But you are right. If you don't know if yours are among those, then it does you no good if you don't know if yours are among the bad ones.
Last edited by '06 Quicksilver Z06; 11-06-2011 at 10:55 AM.
11-06-2011, 10:45 AM
#685
Team Owner
As per the norm for what this forum has become, people twist what they want. The guys were not amused at what people were experiencing, why in the hell would they do that???????? They were amused at some to the attitudes of some of the people, and their reasoning.
As far as the Avatar goes it is my car on the Tail of the Dragon last April, when Jimman and I tried to break some valves on our Z06's. Believe it or not they made three passes on the Dragon, and a 7k road trip to boot.
forOtmypen was considerate enough to contact me to use the pic for his avatar.
Cheers.....
Last edited by Varmit; 11-06-2011 at 11:11 AM.
11-06-2011, 12:32 PM
#686
Tech Contributor
Member Since: Oct 1999
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After that a trip over to Comp and Lingenfelter to ask questions pertaining to the LS7 valve issue.
First the material for the valve guide used in the Stock OEM is powdered metal; the word metal refers to not just one element but a mix of several elements one including copper. This enables the tailoring of characteristics needed for guide performance. Lingenfelter uses the stock guide material in their builds. If there is an issue with dimensions of the guide and valve the guide is machined to the required spec. They do not recommend Bronze, can’t control the metal characteristics.
Two I asked of the solid stainless steel fix, they rolled their eyes and just shook their head, too heavy and unstable at high rpms in this valve train.
Three why are the valve heads breaking off, their answer from both Comp and Lingenfelter was the only way is either a defective valve which is highly unlikely and piston to valve contact. I asked how that was possible as far as piston contact, answer valve float do to over rev or weak springs. Further discussion on this as to what could cause this and they laughed and said do you really think the drivers will ever admit to that. Not only missed shifts but sudden rpm changes during down shifts that will cause stress. They went on to say it just takes one event to start the process. Tracking and racing a car will fatigue the springs and the float will start to occur at lower rpms.
However, if the springs did weaken and allow valve float to occur sooner, then maybe I could have experienced it before an upshift. If you look at the video I posted showing when my engine let go you can see the tach reaching about 6800 which is a couple of hundred rpm below the limiter. I did feel a vibration similar to hitting the limiter just as I was getting ready to shift, I didn't know what it was but maybe it was valve float which would have allowed a valve to hit the piston. I drove close to the limiter most of the time and actually hit it a few times a day. On almost every lap I would come close to it just running up the back straight at the Glen in 4th gear. Other people shift to 5th to keep the rpms down. This doesn't explain failures on engines where guys regularly short shift just so they don't get near the limiter or upper rpm ranges.
But in some cases is the solution to the problem just replacing valve springs every year?
Bill
11-06-2011, 12:40 PM
#687
Team Owner
I am pretty sure I didn't over rev the engine on downshifts since my only downshift is from 4th to 3rd and that always occurs at a speed less than what cause an overrev of the engine even if I totally screwed up. Even if the valve springs did weaken and reduce the chance of valve float the speed at which the downshift occurs and the rpms reached in 3rd still wouldn't get to the level that valve float would occur on a downshift.
However, if the springs did weaken and allow valve float to occur sooner, then maybe I could have experienced it before an upshift. If you look at the video I posted showing when my engine let go you can see the tach reaching about 6800 which is a couple of hundred rpm below the limiter. I did feel a vibration similar to hitting the limiter just as I was getting ready to shift, I didn't know what it was but maybe it was valve float which would have allowed a valve to hit the piston. I drove close to the limiter most of the time and actually hit it a few times a day. On almost every lap I would come close to it just running up the back straight at the Glen in 4th gear. Other people shift to 5th to keep the rpms down. This doesn't explain failures on engines where guys regularly short shift just so they don't get near the limiter or upper rpm ranges.
But in some cases is the solution to the problem just replacing valve springs every year?
Bill
However, if the springs did weaken and allow valve float to occur sooner, then maybe I could have experienced it before an upshift. If you look at the video I posted showing when my engine let go you can see the tach reaching about 6800 which is a couple of hundred rpm below the limiter. I did feel a vibration similar to hitting the limiter just as I was getting ready to shift, I didn't know what it was but maybe it was valve float which would have allowed a valve to hit the piston. I drove close to the limiter most of the time and actually hit it a few times a day. On almost every lap I would come close to it just running up the back straight at the Glen in 4th gear. Other people shift to 5th to keep the rpms down. This doesn't explain failures on engines where guys regularly short shift just so they don't get near the limiter or upper rpm ranges.
But in some cases is the solution to the problem just replacing valve springs every year?
Bill
DH
11-06-2011, 12:40 PM
#688
Burning Brakes
Member Since: Jun 2010
Location: Phoenix Arizona
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The ECM doesn't log that, (except maybe in the 09+ cars) the "black box" does that. The ECM doesn't record data in the older style PCM cars.. that's why you need HPTuners or something to read the data in real time and record it yourself.
11-06-2011, 01:45 PM
#689
Melting Slicks
From their store/catalog;
"This 65g lightweight beehive spring is Katech's default for all engine packages. Optron valvetrain dynamics testing revealed this spring was the best choice to keep lightweight valves such as LS6 and LS7 in control. "
11-06-2011, 02:10 PM
#690
Le Mans Master
I can speak for myself. I simply have no desire to be drawn into these arguments. People are free to think what they want of the problem. I honestly do not care one way or they other. Either drive the car or sell I don't care.
As per the norm for what this forum has become, people twist what they want. The guys were not amused at what people were experiencing, why in the hell would they do that???????? They were amused at some to the attitudes of some of the people, and their reasoning.
As far as the Avatar goes it is my car on the Tail of the Dragon last April, when Jimman and I tried to break some valves on our Z06's. Believe it or not they made three passes on the Dragon, and a 7k road trip to boot.
forOtmypen was considerate enough to contact me to use the pic for his avatar.
Cheers.....
As per the norm for what this forum has become, people twist what they want. The guys were not amused at what people were experiencing, why in the hell would they do that???????? They were amused at some to the attitudes of some of the people, and their reasoning.
As far as the Avatar goes it is my car on the Tail of the Dragon last April, when Jimman and I tried to break some valves on our Z06's. Believe it or not they made three passes on the Dragon, and a 7k road trip to boot.
forOtmypen was considerate enough to contact me to use the pic for his avatar.
Cheers.....
What's frustrating is here we are, discussing and debating possible causes, then you and Jimman actually talk to some GM engineers then act all coy about what they told you.
11-06-2011, 02:24 PM
#691
I can't speak for the other engine builders here, but I believe that Katech still promotes the use of the (stock) GM beehive valve spring for many if not most of their engines. My Katech engine has the large GM Stage III cam, and Katech used new stock beehive springs for the build.
From their store/catalog;
"This 65g lightweight beehive spring is Katech's default for all engine packages. Optron valvetrain dynamics testing revealed this spring was the best choice to keep lightweight valves such as LS6 and LS7 in control. "
From their store/catalog;
"This 65g lightweight beehive spring is Katech's default for all engine packages. Optron valvetrain dynamics testing revealed this spring was the best choice to keep lightweight valves such as LS6 and LS7 in control. "
As an endurance - focused road race engine, what would your recommendation be for service rebuilds (hours), if this was used as a track day car?
With the follow up question.....
Sorry of this is a dumb question, but do you mean 30 hrs of WOT or just 30 hours in total track time? I've always been confused by this
11-06-2011, 02:26 PM
#692
I don't see how relaying what you heard gets you drawn into an argument, though I don't know why you'd even bother to post in this thread to begin with it you were worried about that.
What's frustrating is here we are, discussing and debating possible causes, then you and Jimman actually talk to some GM engineers then act all coy about what they told you.
What's frustrating is here we are, discussing and debating possible causes, then you and Jimman actually talk to some GM engineers then act all coy about what they told you.
I agree spill it.....
I should have went to SEMA....
11-06-2011, 02:29 PM
#693
Team Owner
I don't see how relaying what you heard gets you drawn into an argument, though I don't know why you'd even bother to post in this thread to begin with it you were worried about that.
What's frustrating is here we are, discussing and debating possible causes, then you and Jimman actually talk to some GM engineers then act all coy about what they told you.
What's frustrating is here we are, discussing and debating possible causes, then you and Jimman actually talk to some GM engineers then act all coy about what they told you.
I was merely relaying some ideas passed on by the people who do this for a living. Wanna get upset, take it out on them. If these same people were supporting your cause we would not be having this conversation.
So hope you the best with you defective products.
11-06-2011, 02:34 PM
#694
Team Owner
Member Since: Apr 2001
Location: Elmhurst, IL (West Suburb of Chicago) & Home of MEGA Horsepower
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St. Jude Donor '06
Bill,
Good post, and I think its a no brainer that for those who are tracking there car at least 5 times a year, that swapping out to new valve springs every year, will go a long way in preventing some of these failures (concerning dropped valves), as it just makes really good logical sense to do so (and that valve float could be occurring on those LS7 engines being tracked hard).
11-06-2011, 03:08 PM
#695
Le Mans Master
Sorry to have bothered you, I was under the impression this was an open forum. I will leave you automotive elite's to your discussions.
I was merely relaying some ideas passed on by the people who do this for a living. Wanna get upset, take it out on them. If these same people were supporting your cause we would not be having this conversation.
So hope you the best with you defective products.
I was merely relaying some ideas passed on by the people who do this for a living. Wanna get upset, take it out on them. If these same people were supporting your cause we would not be having this conversation.
So hope you the best with you defective products.
Hell of a contribution. Way to go.
11-06-2011, 04:10 PM
#696
Melting Slicks
I agree with those guidelines and I'm not exactly sure why (or if) you are pointing them out to me - I have made several posts in these threads regarding recommended maintenance for track cars somewhere between 30-40 hours of track time. Perhaps you are pointing it out for other folks in these threads?
With that said, my engine has about 20 hours of track time so it will be time for some checks pretty soon. In talking with Jason about some upcoming power upgrades, including some headwork, he said they can check my spring pressures to see if they are candidates for replacement.
Last edited by Everett Ogilvie; 11-06-2011 at 08:16 PM.
11-06-2011, 04:13 PM
#697
Le Mans Master
Thread Starter
Bill,
Good post, and I think its a no brainer that for those who are tracking there car at least 5 times a year, that swapping out to new valve springs every year, will go a long way in preventing some of these failures (concerning dropped valves), as it just makes really good logical sense to do so (and that valve float could be occurring on those LS7 engines being tracked hard).
Good post, and I think its a no brainer that for those who are tracking there car at least 5 times a year, that swapping out to new valve springs every year, will go a long way in preventing some of these failures (concerning dropped valves), as it just makes really good logical sense to do so (and that valve float could be occurring on those LS7 engines being tracked hard).
Plus everyone with milled heads would be dropping valves everywhere since they decreased the clearance.
Last edited by whatcop?; 11-06-2011 at 04:17 PM.
11-06-2011, 04:43 PM
#698
Tech Contributor
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Bill
11-06-2011, 09:24 PM
#700
Think about the relationship of the valve events to piston travel during the exh/int strokes and it will make sense.