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***Build Date/VIN Analysis of LS6 Valve Spring Failures***
First of all, the background for this thread can be found here:
c5-z06-discussion/list-of-c5z06s-with-failed-valvesprings-not-always-high-mileage-pics.html Before asking common questions like, "Which springs should I buy?", or "What else should I replace at the same time?", or "How much will it cost?", read through that thread first. The answers you're looking for are probably already in there. Secondly, a big thanks goes out to Steve Doten Motorsports and all the individuals who contributed data or information during this study. Now for the main event. I've researched Corvette Forum and Z06Vette.com, and found a total of 163 reported valve spring failures. Most of the owners were contacted, and I have the build month and/or VIN information of 77 of the broken valve springs. This is definitely a large enough data set to confidently make some broad conclusions. First, the number of reported valve spring failures for each model year is plotted. There are 5 for 2001, 94 for 2002, 59 for 2003, and 5 for 2004. Clearly, 2002 and 2003 deserve a closer look. https://farm6.staticflickr.com/5452/...a14ba9df_o.png This plot breaks down the build run for 2002 and 2003 models into 4-month segments. Something clearly went wrong in the spring and summer of 2002. https://farm8.staticflickr.com/7738/...c85551cf_o.png But this still doesn't give us an actual probability, or likelihood, of valve spring failure for any specific group. Which brings us to the final plot. Since there is no way of knowing what fraction of the total population is represented by the data set, we can't determine probabilities in an absolute sense. However, we can determine probabilities in relative terms. This plot compares different groups in a true per capita sense, based on the number of reported spring failures divided by the number of Z06's built during each time segment. https://farm8.staticflickr.com/7797/...de1831a2_o.png Using 2001 + 2004 models as our baseline low risk group, this plot shows that: - Early 2002 models (VINs under 20000) are over 6 times as likely to experience a valve spring failure than the baseline. - Late 2002 models (VINS over 20000) and early 2003 models (VINs under 09000) are 20 times more likely than the baseline to experience a valve spring failure. This is the HIGHEST RISK group, aka the Danger Zone. - Late 2003 models (VINs over 09000) are over 3 times as likely to experience a valve spring failure than the baseline. These numbers represent the last 5 digits of the VIN. Both the VIN and build month can be found on the driver's side door jamb. |
Skyavonee,
Want to commend you on your work putting the pareto's together. Thanks for the support! |
I also want to give a special thanks and thumbs up to Skyavonee.:thumbs:
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Ditto what the others have said. Appreciate the effort you have put into this.
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awesome write up man... i am investigating my setup.... I have an 02 so I hope I am ok!
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Well done Mike, we should all chip in for your next mod.
Based on this project I did my springs on My May 2002 built Z06 as PM. Looks like I would have been in the highest risk group. Ed |
Good work gathering all the data and trying to make sense of it all. :thumbs:
My recommendation for anyone who has a 2002 or 2003 Z06 is to seriously think about replacing the OEM springs ... then you know the risk is mitigated. |
Thanks for the tremendous work and data collection. I've been wanting to do something similar for quite some time.
The question that I'm interested in is who was the spring supplier during this period? Does anyone know someone who worked at the facility? Was there a bad batch, know/unknown manufacturing defect? Did a batch of springs get their lube inadvertently rinsed off and had surface corrosion develop during shipping storage etc.? Was a rookie on the line when these springs were made? I guess the list of questions could go on and on, but perhaps someone here knows someone in the loop. I'm not looking to blame or point fingers but rather solve the mystery of why a certain batch went bad? Think of it as CSI Z06:D |
Originally Posted by doveboat
(Post 1580982069)
Well done Mike, we should all chip in for your next mod.
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Analysis was well done and is an easy read.
Thanks for all your hard work. \db2 carolina |
I'll echo the others in saying thank you & excellent work! :cheers:
Was following the other thread and am having mine replaced with Pac 1218's next Monday. Looking over your charts, I feel relieved driving my '03 until then (11/6/2002 build date) :cool: |
Originally Posted by Trash
(Post 1580982504)
Thanks for the tremendous work and data collection. I've been wanting to do something similar for quite some time.
The question that I'm interested in is who was the spring supplier during this period? Does anyone know someone who worked at the facility? Was there a bad batch, know/unknown manufacturing defect? Did a batch of springs get their lube inadvertently rinsed off and had surface corrosion develop during shipping storage etc.? Was a rookie on the line when these springs were made? I guess the list of questions could go on and on, but perhaps someone here knows someone in the loop. I'm not looking to blame or point fingers but rather solve the mystery of why a certain batch went bad? Think of it as CSI Z06:D |
It looks like my 02 Z06 falls into the 6/01 to 9/01 category since my actual build date is 9/01.
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great work, and definitely is going to help with my search!
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Awesome work Skyavonee. Thanks for taking the time to do this.
In the data your collected did you happen to record the color of the springs that fail? Just wondering if my theory that yellow springs are the bad "batch" GM used in the timeframe you identified. My Z06 is in the post August group, bone stock with non-yellow springs from factory. Nov 2002 build date. |
Originally Posted by Atok
(Post 1580987710)
In the data your collected did you happen to record the color of the springs that fail? Just wondering if my theory that yellow springs are the bad "batch" GM used in the timeframe you identified. My Z06 is in the post August group, bone stock with non-yellow springs from factory. Nov 2002 build date.
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Add me to the list. Here is my thread. Build date is 5/02. Springs were non-yellow.
http://forums.corvetteforum.com/c5-t...re-inside.html |
Originally Posted by KLR Z06
(Post 1580991167)
Add me to the list. Here is my thread. Build date is 5/02. Springs were non-yellow.
http://forums.corvetteforum.com/c5-t...re-inside.html In order to minimize work on my end, I'll update my numbers and graphs every couple weeks, instead of every single time a new data point arises. I'm hoping/expecting there are others like you out there that come forward with more build dates. Every additional data point - no matter which group it belongs to - improves the accuracy of the statistics. :thumbs: |
A big thanks goes out to the following CF members who submitted build date info, either directly or indirectly.
2002rich 24hr Z06 250kicker 2K3Z06 ACE10000D Aerodan aquachuck1 bignasty bikerbabcock bing44 Black 02 BlackZ2003 blazer427X3 Blue Angel Boilerdawg callie454 charlie808 CrazyInBlack dart.deanda dbaker DEAN'S98@11.13 Dude. Eric Reeves fredl11 IH8PONYS janky Jmzo6 KLR Z06 levettegrl liquidforce917 ltborg MattyMaxMac MikeD33 MIKER MDS24K Mooty1 MustGoFaster Mwortham MY03C5Z NBM LS1 M6 neetstuff55 Old as Dirt Quicksilver Z06 redroket Robert R1 rolexfix SoCalSteve Sothpaw2 Speeed-Racer SteveDotenMotorsports Sw48 Titan22 Tom03Z06 Torqaholic tricep varkwso VladWalt Wild Horzes Wire5150 WS-6SLEEPER Xx_Black-out Yakisoba ZeeOhSix597 zeke2u Any more data out there? :bigears |
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