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Thread: LS7 and the question of valve guide wear, bulletin

  1. #1

    Default LS7 and the question of valve guide wear, bulletin

    Much confusion has been out there about LS7 and valve stem to guide clearance.

    We are instructed by TSB 13.06.01.001 to follow accurate service guidelines to evaluate and troubleshoot LS7. Below is the document so you can see for yourself.

    Some owners of Corvettes equipped with the LS7 7.0L V8 engine may ask your dealership to check their vehicle for valve guide wear because of information that has been distributed on the internet, primarily at Corvette enthusiast sites. Due to these postings, some customers that have not had an issue may ask to have their vehicle checked. If a customer presents their vehicle and requests the valve guides be checked, the following information may be helpful to you and alleviate any concern for your customer.

    Valve Guide Wear / Noise Concerns
    To address any concern the customer may have, listen to the customer’s request and ask the following questions to differentiate if the customer has experienced a correctable engine concern or has anxiety over information they may have read.

    Important: It is important to investigate all concerns and relay good factual information to your customer. If a customer indicates a concern about valve guide wear, it is possible they may have a valid unrelated engine issue, and do not know how to express the actual concern.

    Have you experienced any concerns or difficulties that would indicate an engine problem?
    Is the Check Engine Light ON? Does the vehicle exhibit any starting/running concerns?
    If the concern is noise related, ask for a description of the type of noise heard?
    Once the information is collected, and the nature of the customers concerns are known, here are some guidelines for appropriate actions:

    For any driveability, starting, running or found DTC code issues, if the car is under the respective warranty period, repair the vehicle following normal diagnostics as outlined in the Electronic Service Information (SI). If the vehicle is out of the warranty period, explain the available options for the customer.
    If the customer indicated a concern with engine noise, warm the vehicle to operating temperature and compare it to similar vehicles. If the vehicle does not exhibit unusual noises or malfunctions, the customer should be told there is nothing to indicate the need to disassemble the engine to determine valve guide wear. The LS7 is a high performance motor and as such is built with an emphasis on power while retaining the lowest possible noise and vibration characteristics. Some valve train noise may be evident, which is a by product of the performance nature of this engine. General Motors has reviewed paid warranty claims for valve and head replacement for the Corvette LS7 and the numbers of incidents are very low with no indication of an excessive wear issue.
    If the customer’s sole concern is based on information collected over the internet, with no verifiable symptom, and the customer insists the engine be disassembled and verified, it should be explained to the customer that any charges for the inspection would be at the customers expense. Valve guides are an internal engine component subject to wear over the life of the vehicle. If there is excessive wear (beyond the indicated service limit) after the investigation is completed, GM will cover the inspection and repair expense for vehicles covered under the Powertrain Limited warranty.
    Aftermarket Equipment and Valve Guide Wear

    The use of performance engine modifications has been found to accelerate valve guide wear. Replacement aftermarket mechanical parts, or software calibrations, may adversely affect the wear of these and other components. Any modification to the engine of GM vehicles voids the powertrain coverage portion of the vehicle warranty.


    The only accurate way to determine actual stem to guide clearance is with the heads, off the engine and on the bench.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
    Twitter: www.twitter.com/GMvettemechanic

  2. #2
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    LS7 owners should also keep in mind that they will most likely never have this kind of any issue, as it is a very rare occurrence.

    Do not let the internet scare you into thinking that this is a common problem, it is not. Drive them, use them, and enjoy them as they should be.
    20+ years ASE and Honda Master Tech

    1998 black 6 spd convertible

  3. #3
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    Quote Originally Posted by LLC5 View Post
    Do not let the internet scare you into thinking that this is a common problem, it is not.
    There lies the biggest problem...too many "S*it House Lawyers, Arm Chair Quarterbacks, and Below Novice Mechanics" out there who scare most folks into this kind of things.
    Like the TV commercial states....Don't believe everything you see, hear or read on the Internet !

    Case in point.....when I brought up the question about splicing brake lines using the proper fittings over at that big Corvette Forum, I got several replies saying... " Against the law in any state to splice brake lines"
    Had to prove them wrong when I scanned the page out of the Factory Service Manual which stated it was OK to do !
    Last edited by SG Lou; 12-27-2014 at 09:29 AM.

  4. #4
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    Quote Originally Posted by SG Lou View Post
    There lies the biggest problem...too many "S*it House Lawyers, Arm Chair Quarterbacks, and Below Novice Mechanics" out there who scare most folks into this kind of things.
    Like the TV commercial states....Don't believe everything you see, hear or read on the Internet !

    Case in point.....when I brought up the question about splicing brake lines using the proper fittings over at that big Corvette Forum, I got several replies saying... " Against the law in any state to splice brake lines"
    Had to prove them wrong when I scanned the page out of the Factory Service Manual which stated it was OK to do !

    I would say don't believe 100% of what you read on the internet until you somehow confirm it.

    The internet is a big old double edged sword for sure........
    20+ years ASE and Honda Master Tech

    1998 black 6 spd convertible

  5. #5

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    HI there,

    In addition to what has already been said, I have had over 50 LS7 engines apart for different reasons.

    I have had 6 engines that had boarderline stem to guide clearance of .003. Average was .0028.

    I have had 3 engines that had over spec of .0037. I have in EVERY CASE OF VALVE GUIDE CLEARANCE ISSUE, there were signs.

    Excessive oil consumption where the spark plugs were fouled, or poor fuel mileage or check engine light.

    There were always symptoms in my cases.

    Accurate education of LS7 is critical as to valve train lift, duration, rocker arm designs and other factors. Extreme detail must be taken when correctly tolerancing an engine.

    YOU NEVER EVER, in any circumstance, do you tolerance engine parts while still assembled, EVER!

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
    Twitter: www.twitter.com/GMvettemechanic

  6. #6
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    I reviewed this post recently and see that most of the information is from 8+ years ago. Are there any updates as time has passed regarding this issue? I've seen all of the internet chatter on this topic and have been biding my time to see if i need to pull the heads off my LS7 to rebuild and/or consider performance modifications. I have a 2011 Z06 Carbon edition with less than 5k miles. I'd appreciate any update...

  7. #7

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    HI there,

    Most internet information is not actually information but vendors badmouthing the LS7 design to sell more things to the Corvette consumer.

    I will give you my hard and fast rules to obtain the BEST out of your LS7.

    #1, DO NOT MODIFY LS7, This means no tune, no long tube headers, no cold air induction and no exhaust. There should BE ABSOLUTELY NO POWER TRAIN MODIFICATIONS IN ANYWAY, not even spark plugs. I have had 7 fail directly due to lean air fuel ratio when having tunes. This melted the pistons creating the failure.

    #2, Oil changes on regular intervals via the engine oil life monitor. Use the ACDelco UPF48R oil filter for maximum results as this filter is exact recommendations from Corvette engineering for maximum filtration and optimal operation of your lubrication system.

    #3, use common sense when driving, even though the LS7 has a redline of 7000 rpm, you don't need it. Torque peak is 4800 rpm and shifting any higher than 6000 rpm is not necessary and really can cause more problems over time. Using the rev limiter as a shift indicator is not what it is there for and will end up creating stress in the valve train area. I have had a few fail due to this.

    #4, Note your check engine light. If your LS7 has valvetrain issues, it will set a misfire diagnostic trouble code when IDLING first, before you see anything else.

    #5, when in doubt, have your engine oil analyzed. Titanium content will show in the engine oil thus you know if you have intake valve wear.

    On a professional note, I have had over 75 apart for different reasons, 3 have been valve train specific failures. I have done more CAMSHAFTS than I have cylinder heads. I have also 7 LS7 powered vehicles which are TRACK ONLY cars, 4 have over 120,000 miles on them and NONE have had valve train issues.

    If you would like further information, please post up and I would be glad to answer any further questions you have.

    Allthebest Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
    Twitter: www.twitter.com/GMvettemechanic

  8. #8
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    Thank you! Always good to get the facts!

  9. #9
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    Quote Originally Posted by mdsci View Post
    Thank you! Always good to get the facts!

    You chose wisely.


    There is a HUGE difference between watching someone doing a job, hearing or reading about someone doing a job (i.e. journalists and internet), and someone actually DOING the work and seeing the results after the job is finished.


    c4c5 is that that difference, and nothing can substitute for it.
    20+ years ASE and Honda Master Tech

    1998 black 6 spd convertible

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