$projecthp
  • Wiggle Testing: How to Perform On-Engine Test for C6 Corvette LS7 Valve Stem-Guide Clearance
  • Wiggle Testing: How to Perform On-Engine Test for C6 Corvette LS7 Valve Stem-Guide Clearance
  • Wiggle Testing: How to Perform On-Engine Test for C6 Corvette LS7 Valve Stem-Guide Clearance
  • Wiggle Testing: How to Perform On-Engine Test for C6 Corvette LS7 Valve Stem-Guide Clearance

Page 1 of 3 123 LastLast
Results 1 to 15 of 36
  1. #1
    Site Administrator Rob's Avatar
    Join Date
    Sep 2000
    Location
    "Manchestah" NH
    Posts
    13,219
    Corvette(s)
    1990 ZR-1 - Bright Red / Black
    Post Thanks / Like
    Rides
    1

    Default Wiggle Testing: How to Perform On-Engine Test for C6 Corvette LS7 Valve Stem-Guide Clearance



    Rob Loszewski, Owner & Site Administrator
    Corvette Action Center
    Cadillac V-Net
    Cadillac XLR Net
    Torque About It
    Torque Network
    VetteTube
    NCRS Member #27792
    "Let your plans be dark and impenetrable as night, and when you move, fall like a thunderbolt." - Sun Tzu
    1990 Chevrolet Corvette ZR-1 , 350 Stock ZF 6-speed. Stock Bright Red

  2. #2
    Member LLC5's Avatar
    Join Date
    Sep 2004
    Location
    Wa.
    Posts
    2,287
    Corvette(s)
    98 black 6spd convert.
    Post Thanks / Like
    Rides
    0

    Default

    I doubt if GM is going to do any warranty work with a DIY test from an independent shop or an owner, I am sure that it would need to be verified by a certified GM tech along with a tech line or DSM ok to do the work.

    Wonder what flat rate time is for that procedure, or if there is one? To do it correctly is very time consuming, to do it with out bending a valve even more so.....
    Master Technician

    25+ year ASE Master Certified Tech

    22+ year Honda Master Tech

  3. #3
    Member
    Join Date
    Mar 2014
    Location
    Columbus, NC/NE Georgia
    Posts
    2,293
    Corvette(s)
    1997 boosted silver coupe
    Post Thanks / Like
    Rides
    0

    Default

    Hib,
    Kudos for the excellent write up.

    Quote Originally Posted by LLC5 View Post
    I doubt if GM is going to do any warranty work with a DIY test from an independent shop or an owner, I am sure that it would need to be verified by a certified GM tech along with a tech line or DSM ok to do the work.

    Wonder what flat rate time is for that procedure, or if there is one? To do it correctly is very time consuming, to do it with out bending a valve even more so.....
    Oh, I am sure they have one and just as sure one can rebuild a head for less.

    They would use a valve guide bore gage which requires the head to be off and the valves out. A .001' to 1.000" is more for measuring lift or shimming valve springs to set coil spacing at lift. A valve guide bore gage reads increments of .0001".
    Whoosh, and blur

  4. #4
    Member LLC5's Avatar
    Join Date
    Sep 2004
    Location
    Wa.
    Posts
    2,287
    Corvette(s)
    98 black 6spd convert.
    Post Thanks / Like
    Rides
    0

    Default

    I forgot to mention about the great write up and excellent information in my last post, very well done for sure Hib.

    I was thinking the same thing as kpic, by the time you pay someone to do the test properly (and hopefully NOT bend any valves, which is way too easy to do) you could have just invested in the repair. Under warranty though would obviously be a different story, first the test procedure would have to start out as customer pay for the diagnosis at a GM certified dealer, and then hopefully the tech would reach the same test numbers that you previously paid someone (or performed yourself) else to do.

    Either way, excellent article.
    Master Technician

    25+ year ASE Master Certified Tech

    22+ year Honda Master Tech

  5. #5
    Member
    Join Date
    Mar 2014
    Location
    Columbus, NC/NE Georgia
    Posts
    2,293
    Corvette(s)
    1997 boosted silver coupe
    Post Thanks / Like
    Rides
    0

    Default

    My wants and inability to pay for what I wanted was how I learned to turn a wrench.
    Whoosh, and blur

  6. #6
    New Member
    Join Date
    Mar 2007
    Location
    Texas
    Posts
    2
    Post Thanks / Like
    Rides
    0

    Default

    "We recommend wiggle testing any LS-7 which has more than 10,000 miles on it". How was this conclusion arrrived at? Is there data to support the need for this test at 10,000 miles on all LS-7's? If yes, can we ask you to share that information? THANKS!

    Merry Christmas!

  7. #7
    Member
    Join Date
    Jul 2003
    Location
    Aiken,SC
    Posts
    35
    Corvette(s)
    Owned 2003, 2010 GS
    Post Thanks / Like
    Rides
    0

    Default Wiggle Test

    As a person who has limited mechanical skill. What symptoms would I be looking for
    to have to take my car back to the dealer. My 2015 has 1200 miles and is running
    flawlessly.
    Thanks
    Rich
    Aiken SC
    Kobes

  8. #8
    Technical Writer for Internet & Print Media
    Join Date
    Jan 2001
    Location
    CenCoast CA
    Posts
    11,938
    Corvette(s)
    71 04 12 19
    Post Thanks / Like
    Rides
    0

    Default

    Quote Originally Posted by LLC5 View Post
    I doubt if GM is going to do any warranty work with a DIY test from an independent shop or an owner, I am sure that it would need to be verified by a certified GM tech along with a tech line or DSM ok to do the work.

    Wonder what flat rate time is for that procedure, or if there is one? To do it correctly is very time consuming, to do it with out bending a valve even more so.....

    The impetus for writing that article was to "answer" some of the incorrect descriptions of the stem-to-guide test procedure posted in various places around the web. One example of a wiggle test DIY thread that, if followed, results in incorrect measurement is on the Corvette Forum at LS7 Wiggle Test DIY

    The article's main intent was to explain how to do the procedure correctly with the heads on the vehicle. The target audience was DIYs and independent service vendors who are working on an out-of-warranty engine or DIYs who want to prove to GM that their engine has a guide wear problem after a warranty claim is denied with the explanation that the engine is not: making noise, using oil and or turning on its MIL.

    I don't know what the flat rate is, but it may be based on removing the heads from the engine which is the method GM implies in factory service data. If it is based on that, then it's actually going to be pretty high. In spite of the "heads-on" method I discuss in the story being difficult and time-consuming, it's still going to take less time than getting the heads off to measure stem-to-guide clearance. Also, if the point of the test is only to gain evidence to support a warranty claim, you only need to go far enough to find one or two bad guides and you're done. If there's one bad guide or 16 of them, GM is going to replace the heads.

  9. #9
    Technical Writer for Internet & Print Media
    Join Date
    Jan 2001
    Location
    CenCoast CA
    Posts
    11,938
    Corvette(s)
    71 04 12 19
    Post Thanks / Like
    Rides
    0

    Default

    Quote Originally Posted by 7thz16 View Post
    "We recommend wiggle testing any LS-7 which has more than 10,000 miles on it". How was this conclusion arrrived at? Is there data to support the need for this test at 10,000 miles on all LS-7's? If yes, can we ask you to share that information? THANKS!
    In the case of most engines which have the problem, by 10,000 miles you should be able to demonstrate it with measurements. Obviously, some engines have developed bad guides with much less miles on them and some with much more.

    It depends on the rate of guide wear and many things can affect that but the main one is non-concentricity. If the level of non-concentricity is .001 then the guides are going to wear at a rate not much more rapidly than stock. If the level of non-concentricity is .007 then the guides are going to wear really fast.

    Merry Christmas!
    Big ole dittos!
    Last edited by Hib Halverson; 01-01-15 at 11:34 AM. Reason: HTML coding error

  10. #10
    Technical Writer for Internet & Print Media
    Join Date
    Jan 2001
    Location
    CenCoast CA
    Posts
    11,938
    Corvette(s)
    71 04 12 19
    Post Thanks / Like
    Rides
    0

    Default

    Quote Originally Posted by rkoblin View Post
    As a person who has limited mechanical skill. What symptoms would I be looking for
    to have to take my car back to the dealer. My 2015 has 1200 miles and is running
    flawlessly.
    Thanks
    Rich
    Aiken SC
    Your engine does not have the problem.

    The valve guide wear issue affects the LS7 engine in 2006-2013 Z06es. It does not affect the LT1 or LT4 in 2015s.

  11. #11
    Member
    Join Date
    Mar 2014
    Location
    Columbus, NC/NE Georgia
    Posts
    2,293
    Corvette(s)
    1997 boosted silver coupe
    Post Thanks / Like
    Rides
    0

    Default

    rkoblin
    As yours is a 2015, you should not be affected.

    Hello all,
    LS7 Valve guide issue summary:
    Affects a small, number of '08, 09 10 and 11 Z06s
    GM discovered the condition through our cylinder head warranty data involving a very small percentage of our vehicles.
    Through inspection of returned heads, it was determined that a machining error in the valve guide had occurred at our head supplier.
    The quality issue has been contained as of Feb 2011 with 100% inspection of all heads.
    The most common customer complaint has been excessive valve train noise.
    However if the condition is not addressed, it could result in engine failure. To date, where this condition has been observed, it has occurred early in the vehicle life.
    What customers need to know: They should drive and enjoy their vehicles without fear. If their car demonstrates this condition, they are likely to hear unusual valvetrain noise first....
    Stage II LS7 cylinder heads - A visual guide to valve guide wear and CNC upgrades - LS1TECH
    The quote is from GM. The thread has some great pictures. However, after all the work of pulling the heads; I'd replace the guides, valves, and springs.

    "it was determined that a machining error in the valve guide had occurred at our head supplier"

    Doesn't make sense unless they meant when the guides are reamed?? That being said; industry has gone away from listing processes. Or if the drawing states 0.007mm with a certain surface finish and the part meets the requirement; no one cares what process was used.
    Whoosh, and blur

  12. #12
    Member
    Join Date
    Jul 2003
    Location
    Aiken,SC
    Posts
    35
    Corvette(s)
    Owned 2003, 2010 GS
    Post Thanks / Like
    Rides
    0

    Default Wiggle Valves

    Thanks for the answer. I feel better. No one want to have problems with their ride. Thanks again. Happy holiday

    rich
    Aiken SC
    Kobes

  13. #13
    New Member
    Join Date
    Mar 2007
    Location
    Texas
    Posts
    2
    Post Thanks / Like
    Rides
    0

    Default

    [QUOTE=Hib Halverson;1160962]
    Quote Originally Posted by 7thz16 View Post
    "We recommend wiggle testing any LS-7 which has more than 10,000 miles on it". How was this conclusion arrrived at? Is there data to support the need for this test at 10,000 miles on all LS-7's? If yes, can we ask you to share that information? THANKS!

    In the case of most engines which have the problem, by 10,000 miles you should be able to demonstrate it with measurements. Obviously, some engines have developed bad guides with much less miles on them and some with much more.

    It depends on the rate of guide wear and many things can affect that but the main one is non-concentricity. If the level of non-concentricity is .001 then the guides are going to wear at a rate not much more rapidly than stock. If the level of non-concentricity is .007 then the guides are going to wear really fast.

    Big ole dittos!
    Thanks. So the 10K miles is not hard data but as GM states "where this condition has been observed, it has occurred early in the vehicle life". The type of miles (tracking vs. casual city / hwy) would likely impact that as well. As far as the "2006 to 2013 LS-7's", the post quoting GM appears to state that a limited number of '08, 09, 10 and 11's only may be affected.

  14. #14
    Member LLC5's Avatar
    Join Date
    Sep 2004
    Location
    Wa.
    Posts
    2,287
    Corvette(s)
    98 black 6spd convert.
    Post Thanks / Like
    Rides
    0

    Default

    Quote Originally Posted by Hib Halverson View Post
    The impetus for writing that article was to "answer" some of the incorrect descriptions of the stem-to-guide test procedure posted in various places around the web. One example of a wiggle test DIY thread that, if followed, results in incorrect measurement is on the Corvette Forum at LS7 Wiggle Test DIY

    The article's main intent was to explain how to do the procedure correctly with the heads on the vehicle. The target audience was DIYs and independent service vendors who are working on an out-of-warranty engine or DIYs who want to prove to GM that their engine has a guide wear problem after a warranty claim is denied with the explanation that the engine is not: making noise, using oil and or turning on its MIL.

    I don't know what the flat rate is, but it may be based on removing the heads from the engine which is the method GM implies in factory service data. If it is based on that, then it's actually going to be pretty high. In spite of the "heads-on" method I discuss in the story being difficult and time-consuming, it's still going to take less time than getting the heads off to measure stem-to-guide clearance. Also, if the point of the test is only to gain evidence to support a warranty claim, you only need to go far enough to find one or two bad guides and you're done. If there's one bad guide or 16 of them, GM is going to replace the heads.



    It is a very good article with excellent information.

    Never thought about the "after a warranty claim is denied" aspect. This would be a good way to possibly get a claim started after a denial.
    Master Technician

    25+ year ASE Master Certified Tech

    22+ year Honda Master Tech

  15. #15
    Member 73shark's Avatar
    Join Date
    Jun 2007
    Location
    KC, MO area
    Posts
    603
    Corvette(s)
    1973 Orange Metallic L-82 Coupe
    Post Thanks / Like
    Rides
    0

    Default

    Anyone have a clue as to what the "machining error" was?

    Great write-up!
    Save the wave

Page 1 of 3 123 LastLast

Similar Threads

  1. Valve stem seals (again!)
    By boblx2a in forum C4 Technical and Performance
    Replies: 7
    Last Post: 10-04-06, 07:59 PM
  2. Valve Stem Question
    By hcolon in forum C5 General Discussion
    Replies: 8
    Last Post: 07-18-06, 09:17 PM
  3. Valve stem
    By bling vette in forum C6 General Discussion
    Replies: 8
    Last Post: 04-26-06, 11:54 AM
  4. Valve stem
    By bling vette in forum C5 General Discussion
    Replies: 1
    Last Post: 02-18-06, 06:33 PM
  5. Valve stem caps
    By TheLabattMan in forum C5 Technical and Performance
    Replies: 2
    Last Post: 06-26-02, 12:03 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •