skyavonee

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.




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.




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.



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

Here are the afflicted forum members:

03QuicksilverZ06 (2003, broke TWO) - corvetteforum.com/1554071911-post7.html
Chuck Harmon (2002) - corvetteforum.com/1553596043-post1.html
game on (2002, broke TWO) - corvetteforum.com/1551985249-post12.html
Diamond (2002, broke TWO) - corvetteforum.com/1551987088-post15.html
fasterz06 (2002) - corvetteforum.com/1552017557-post16.html
R-Z06-LS6 (2002) - corvetteforum.com/1548400522-post1.html
Wolf Dog (2002) - corvetteforum.com/1548401560-post2.html
JackD (2003) - corvetteforum.com/1558385991-post1.html
redroket (2002) - corvetteforum.com/1558388787-post4.html
Steve Row (2002) - corvetteforum.com/1557649284-post10.html
rb185afm (2002) - corvetteforum.com/1566731486-post11.html
2002rich (2002) - corvetteforum.com/1566749527-post19.html
Diceman9 (2002) - corvetteforum.com/1566774546-post21.html
levettegrl (2002, broke TWO) - corvetteforum.com/1567763074-post26.html
tricep (2002) - corvetteforum.com/1567755378-post24.html
stradaboy1 (2001) - corvetteforum.com/1567778960-post29.html
ZEEEEOOOOSIC (2003) - corvetteforum.com/1567327242-post1.html
Speeed-Racer (2004) - corvetteforum.com/1562651752-post8.html
yakisoba (2002) - corvetteforum.com/1565473616-post10.html
BLACKONBLACKZ06 (2001) - corvetteforum.com/2207336-post1.html
Wild Horzes (2003) - corvetteforum.com/1565403544-post37.html
Numb (2002) - corvetteforum.com/1564765694-post13.html
Bill Hilt (2003) - corvetteforum.com/1562591407-post5.html
urwtrdrm (2002) - corvetteforum.com/1561431530-post27.html
blueangelfightr (2003) - corvetteforum.com/1560672903-post1.html
IH8PONYS (2003) - corvetteforum.com/1554740561-post16.html
mcobra01 (2002) - corvetteforum.com/1566588397-post27.html
mwortham (2002) - corvetteforum.com/1566619558-post40.html
SoCalSteve (2003) - corvetteforum.com/1566691403-post52.html
jmzo6 (2002) - corvetteforum.com/1566717469-post58.html
MIKER (2002) - corvetteforum.com/1571078258-post61.html
6xVETTE (2002) - corvetteforum.com/1571099053-post71.html
Badd LS6 (2004) - corvetteforum.com/1573173513-post4.html
Xx_Black-out (2002) - corvetteforum.com/1573225295-post16.html
sw48 (2003) - corvetteforum.com/1573236507-post25.html
StrongArm73 (2002) - corvetteforum.com/1573265055-post28.html
Kevin 64 (2002) - corvetteforum.com/1573447828-post42.html
02Z06clark (2002) - corvetteforum.com/1571093343-post37.html
Quicksilver Z06 (2002) - corvetteforum.com/1571093606-post38.html
Robert R1 (2002) - corvetteforum.com/1571599783-post18.html
aquachuck1 (2002) - corvetteforum.com/1580554179-post8.html
WS-6SLEEPER (2002) - corvetteforum.com/1571848754-post141.html
kru510 (2002) - corvetteforum.com/1571976414-post162.html
Tom03Z06 (2003) - corvetteforum.com/1572527332-post187.html
ckolben (2002) - corvetteforum.com/1572600951-post206.html
Blue Angel (2002) - corvetteforum.com/1571946902-post22.html
2K3Z06 (2003) - corvetteforum.com/1575145192-post1.html
ltborg (2002, broke TWO) - corvetteforum.com/1575295560-post36.html
swollix (2002) - corvetteforum.com/1575166554-post1.html
z06sicz (2002) - corvetteforum.com/1573753647-post3.html
Sinking (2002) - corvetteforum.com/1573756040-post6.html
Bracati (2003) - corvetteforum.com/1578945109-post1.html
Woodytick (2003) - corvetteforum.com/1578955182-post15.html
Bob Thomas (2003) - corvetteforum.com/1578957672-post16.html
diddiyo (2003) - corvetteforum.com/1579154980-post7.html
Torqaholic (2003) - corvetteforum.com/1580551681-post1.html
24hr Z06 (2004) - corvetteforum.com/1552384505-post9.html
sandsman1959 (2002) - corvetteforum.com/1571211527-post11.html
mooty1 (2002) - corvetteforum.com/1568787465-post1.html
88yellow (2003) - corvetteforum.com/1579065735-post80.html
Evil Oil Apologist (2003, broke TWO) - corvetteforum.com/1579564170-post95.html
bing44 (2002, broke TWO) - corvetteforum.com/1579634476-post108.html
gmblack3 (2001) - corvetteforum.com/1550992965-post1.html
SteveDotenMotorsports (2002) - corvetteforum.com/1580356275-post1.html
SteveDotenMotorsports (2003) - corvetteforum.com/1580613834-post11.html
aerodan (2002) - corvetteforum.com/1580682453-post19.html
aerodan (2002) - corvetteforum.com/1580682466-post20.html
boilerdawg (2003) - corvetteforum.com/1580784984-post40.html
dart.deanda (2003, broke THREE) - corvetteforum.com/1580816085-post60.html
dbaker (2002) - corvetteforum.com/1580830310-post66.html
Z06scentair (2002) - http://forums.corvetteforum.com/1580852760-post78.html
rjs96gt (2002, broke TWO) - corvetteforum.com/1576833037-post4.html
lwise4 (2002) - corvetteforum.com/1576873585-post42.html
sothpaw2 (2003) - corvetteforum.com/1565464268-post7.html
MY03C5Z (2003) - corvetteforum.com/1580860952-post84.html
Popclutch (2002, broke TWO) - corvetteforum.com/1571591152-post36.html
blazer427x3 (2002), broke TWO) - corvetteforum.com/1571459357-post22.html
02Z06EB (2002) - corvetteforum.com/1577101570-post18.html
bikerbabcock (2002) - corvetteforum.com/1579737246-post1.html
JACSZ06 (2002) - corvetteforum.com/1546254901-post1.html
girlyZ0sick (2003) - corvetteforum.com/1555678509-post1.html
Mac 108 (2003) - corvetteforum.com/1574433915-post1.html
QSZOH6 (2002) - corvetteforum.com/1575181427-post17.html
Black 02 (2002 - corvetteforum.com/1580967599-post128.html
KLR Z06 (2002) - corvetteforum.com/1575111757-post1.html
racerx_72 (2002) - corvetteforum.com/1572483676-post39.html
Hex$cyn (2002) - corvetteforum.com/1573332944-post57.html
RANsTRZ06 (2004) - corvetteforum.com/1581019575-post21.html
VladWalt (2003) - corvetteforum.com/1581047859-post1.html
neetstuff55 (2002) - corvetteforum.com/1581105354-post1.html
MikeD33 (2003) - corvetteforum.com/1581100479-post33.html
varkwso (2002) - corvetteforum.com/1581217800-post35.html
ACE10000D (2003) - corvetteforum.com/1581334858-post190.html
Old as Dirt (2002) - corvetteforum.com/1581394155-post196.html
bignasty (2003) - corvetteforum.com/1582161498-post21.html
fredl11 (2002) - corvetteforum.com/1582459997-post4.html
Titan22 (2003) - via PM
CrazyInBlack (2003) - corvetteforum.com/1582908110-post1.html
liquidforce917 (2003) - corvetteforum.com/1583158043-post107.html
NBM LS1 M6 (2002) - corvetteforum.com/1583538986-post166.html
Eric Reeves (2002) - corvetteforum.com/1583543832-post175.html
MustGoFaster (2003) - corvetteforum.com/1583561878-post187.html
DEAN'S98@11.13 (2003) - corvetteforum.com/1583577182-post3.html
Wire5150 (2002) - corvetteforum.com/1584167456-post231.html
callie454 (2003) - corvetteforum.com/1584181719-post237.html
pflynn (2003) - corvetteforum.com/1584773819-post1.html
charlie808 (2003) - corvetteforum.com/1584978889-post264.html
BlackZ2003 (2003) - corvetteforum.com/1586604965-post348.html
nbelingheri (2003) - corvetteforum.com/1586253370-post249.html
zeke2u (2003) - corvetteforum.com/1586253370-post249.html
MDS24K (2003) - corvetteforum.com/1586253370-post249.html
250kicker (2003) - corvetteforum.com/forums/c5-z06-discussion/3069497-build-date-vin-analysis-of-ls6-valve-spring-failures-19.html#post1588029637
Dude. (2004)
jon boring (2002)
jakdeefl (2003)
janky (2003)
ZeeOhSix597 (2003)
rolexfix (2002)
MattyMaxMac (2003)

And from Z06Vette.com:

F1_SS (2001)
DucZ06 (2001)
TackDaBoat (2002)
billco2 (2002, broke TWO)
GotXqss (2002, broke THREE)
02PdiddyZ06 (2002)
Pony Tamer (2002)
LostCause (2002)
Dr.Electron (2002, broke TWO)
blkZ06 (2002)
Tom Fuscaldo (2002)
JedAlbano (2002)
GEORGE MANNING (2002)
Polar Bear (2002)
Zed (2002)
TCSZ06 (2002)
JameyZ28 (2002)
Z06rydah (2003)
conrad damon (2003)
Tjason25 (2003)
JackisChaos (2003)
brotha03Z06 (2003)
Ness70 (2003)
BLKWIDOW (2003, broke TWO)
chelmreich (2003, broke TWO)
Larszo6 (2002)

z06scentair

Skyavonee,

Want to commend you on your work putting the pareto's together.

Thanks for the support!

GenerationX1

I also want to give a special thanks and thumbs up to Skyavonee.

C5Longhorn

Ditto what the others have said. Appreciate the effort you have put into this.

Vipernj00

awesome write up man... i am investigating my setup.... I have an 02 so I hope I am ok!

doveboat

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

ZeeOSix

Good work gathering all the data and trying to make sense of it all.

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.

Trash

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

skyavonee

I like that deal! In fact, I'm about to drop my car off at RPM for some cam/valvetrain work.

dbaker

Analysis was well done and is an easy read.

Thanks for all your hard work.

\db2
carolina

Z06Durham

I'll echo the others in saying thank you & excellent work!

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)

C5_LS6

I just changed my springs last Friday and still have the originals in a box. I'm wondering if it's possible to take these springs to a steel company and have them melted down to get the properties from them, or maybe we need all the (so called high risk) defected springs from everybody and put them in a box and have them sent for a properties test. This could help determine if in fact the metal in the springs were defective or not.

GenerationX1

It looks like my 02 Z06 falls into the 6/01 to 9/01 category since my actual build date is 9/01.

getkong

great work, and definitely is going to help with my search!

Atok

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.

skyavonee

Not many people posted pictures or cited spring color. But of those that did, yellow was definitely the most common.

thechosenone

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

skyavonee

Another one from the Danger Zone...

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.

skyavonee

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?