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  1. #1
    Join Date
    Jan 2014
    Posts
    2

    Default LS7 wiggle test

    With all the "sky is falling" posts over on the other site concerning valve guide wear, I'm wondering if I should bring my Z in to the dealer and have them take a look. Wondering if C4C5 has done any at his dealership and if so, how many LS7's have had issues? Any members here results? Not looking to start a LS7 bash here, just get info fo an educated decision. Thanks all
    Bill

  2. #2

    Default

    HI there,

    'wiggle test" is a very vague term when it comes to LS7 inspection and diagnostics of any cylinder head valve guide conditions.

    Now, I have inspected over 40 LS7 engines and in that time, have only found 3 that had any measureable valve guide wear. 2 had incorrectly machine cylinder heads.

    The education starts with any abnormal engine noises, using either a mechanics stethescope or listening device. Also, inspection of the spark plugs and validating oil consumption are also parts to accurate diagnostics of any 427 condition. Scanning of the engine control module for any type of misfires or fuel trim tables will ALSO show possible conditions.

    On the other side of the coin, internet theory is idiotic for the most part. Most are from manufacturers using scare tactics to sell cylinder head packages.

    Facts are: Yes, there have been some mismachined cylinder heads from GM. Yes, there have been a few valve guide wear issues, but no MORE than any other Generation 3 or Generation 4 small block engine.

    Truthfully, NOONE really knows how many REAL problems have been found with LS7 even if you are talking about vehicles repaired under GM powertrain warranty.

    An educated technician, with accurate diagnostic capability and correct mechanical tolerancing of your engine will be able to tell you if you do or do NOT have an issue.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  3. #3
    Join Date
    Mar 2018
    Posts
    1

    Default

    Quote Originally Posted by c4c5specialist View Post
    HI there,

    'wiggle test" is a very vague term when it comes to LS7 inspection and diagnostics of any cylinder head valve guide conditions.

    Now, I have inspected over 40 LS7 engines and in that time, have only found 3 that had any measureable valve guide wear. 2 had incorrectly machine cylinder heads.

    The education starts with any abnormal engine noises, using either a mechanics stethescope or listening device. Also, inspection of the spark plugs and validating oil consumption are also parts to accurate diagnostics of any 427 condition. Scanning of the engine control module for any type of misfires or fuel trim tables will ALSO show possible conditions.

    On the other side of the coin, internet theory is idiotic for the most part. Most are from manufacturers using scare tactics to sell cylinder head packages.

    Facts are: Yes, there have been some mismachined cylinder heads from GM. Yes, there have been a few valve guide wear issues, but no MORE than any other Generation 3 or Generation 4 small block engine.

    Truthfully, NOONE really knows how many REAL problems have been found with LS7 even if you are talking about vehicles repaired under GM powertrain warranty.

    An educated technician, with accurate diagnostic capability and correct mechanical tolerancing of your engine will be able to tell you if you do or do NOT have an issue.

    Allthebest, Paul
    I know this is an older post but I’m wondering if your opinion has changed since you wrote this?

  4. #4
    Join Date
    Jul 2018
    Location
    CA
    Posts
    4

    Default

    Quote Originally Posted by Craighole View Post
    I know this is an older post but I’m wondering if your opinion has changed since you wrote this?
    Sir,

    I will not attempt to answer for C4/C5 Spec, however I was fortunate to be the only student who arrived early for his C5-C6 Diagnostic class at Bloomington Gold '18. So we were one on one discussing the valve guide issue on C6 Z06's (since I drove mine from CA to Indy for the event!).

    He was pleased to know that my Z06 was still as the factory built it...no modifications, none, bone stock, and he HIGHLY recommended that I keep it that way. No mods, none!

    My opinion of our conversation was as he wrote in the above response and additionally, that my chances of something else breaking on the engine before the valve train issue.

    I left feeling very comfortable with his explanation AND his very high confidence in the LS7.
    Hope this helps.

    Enjoy your Corvette!

    Ron '08 Z06 31k mi.


    Sent from my SM-G955U using Tapatalk

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