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  • LS7 Valve Guide Wear Issue
  • LS7 Valve Guide Wear Issue
  • LS7 Valve Guide Wear Issue
  • LS7 Valve Guide Wear Issue

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  1. #16
    Member Iroc2Vette's Avatar
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    I think it's a good way to see what's happening inside the engine without any disassembly. It's kind of like having blood work done. I'll post it as soon as I get the results back. Should be very interesting.
    "Aerodynamics are for people who can't build engines." -Enzo Ferrari

  2. #17
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    Quote Originally Posted by 2VettesMike View Post
    "....the suspect period was July, 2008 to March, 2009."

    Mike
    Mine is a 2009, how do I find if I'm in this group? Where's the dates? Thanks.

    Great read Hib, thanks.

  3. #18
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    Quote Originally Posted by Hib Halverson View Post
    GM expressed all values metric, where I thought it would be easier for most CAC members to understand, I converted it to English. The CMM I watched do an LS7 head was a Zeiss Prismo. GMPT's Inspection Department is big enough that Zeiss has a resident engineer there. He was present during this session and said the Prismo in which that head was installed was accurate to 2 microns/300-mm.

    Hib,
    I used metric as that is what I work with everyday. We have a Zeiss Accura and Contura. I am in design not the measurement lab. So to me, the .002/300 means accurate within .002 over a span of 300mm.
    I believe that would be 2.5um/300mm (sorry the site software does not allow the use of alt followed by 230 which is the funny u followed by m, so I cannot enter micrometers )
    Here are the Prismo's specifications.
    http://www.optecgroup.com/upload/ibl...smo_150dpi.pdf
    There are 3 models of Prismo; 5+7, 10 X=1200 and 10 X =1600 and the accuracy depends on which model.

    The weakness of the wiggle test. If two playing cards have a bore of 10.002mm diameter and we insert a rod with a diameter of 10.000mm. The tilt or angle of the rod will be the same no matter if the cards are separated by 10mm or 100mm. The .002mm is significantly smaller than valve to guide clearances.

    "Generally speaking, the intake valve stem-to guide clearance for most passenger cars ranges from .001 to .003 in., and .002 to .004 in. for exhaust guides (which generally require .0005 to .001 in. more clearance than the intakes for thermal expansion). Diesel engines as a rule have looser specs on both intake and exhaust guides than gasoline engines, and heads with sodium-filled exhaust valves usually require an extra .001 in. of clearance to handle the additional heat conducted up through the valve stems."

    The problem is 2 circles have a line of contact. At maximum tilt there would be very little wiggle and a lot more clearance. Therefore, depending of the spacing between the two lines of contact; with some engines the wiggle test could be accurate or quite inaccurate. It is clearance which is the problem, not wiggle.

    Whoosh, and blur

  4. #19
    Member Iroc2Vette's Avatar
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    Quote Originally Posted by Tuna View Post
    Post it here. I've got 26K on my LS7 and the oil has been changed 3 times. Maybe I ought to have my oil tested by a lab to see how it's doing.
    Tuna...I screwed up on sending out the last bottle of oil for analysis. I just dropped it into a postal pickup box and it never got to the lab. I should've hand delivered it to the post office to register it as a liquid and flammable. I'll be due for another oil change (DIC says I'm below 30%) and I ordered another kit.

    I will say I now have 36K mi and so far, the engine is neither using any oil nor developed any valve train noises. So far, so good. I drive it whenever the weather is decent. Even if it's just to the gym. But, I'm going to give the analysis another try. That's why I haven't posted anything here yet. Sorry for the delay....
    "Aerodynamics are for people who can't build engines." -Enzo Ferrari

  5. #20
    LS7 Valve Guide Wear Issue Tuna's Avatar
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    My LS7 has just over 30K now. It is not using oil nor is it making any valve train noise.
    Now that I'm retired and not driving to work every day, the Vette and the V Wagon are getting a lot less use also. Too bad, driving either is a lot of fun.
    Tuna
    My Novels:
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    Murder mysteries!


  6. #21
    Member Iroc2Vette's Avatar
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    I just sent off the oil sample yesterday. The instructions said I could just put it in the envelope and just drop it into any mail receptacle. Hopefully, I'll get a report in the next couple of weeks. I put on a special note that TI and FMPM was of greatest interest due to the valve drop issues of the earlier engines. Don't know if that'll mean anything or not. This should be very telling. It's like doing a blood test on the engine. I had about 8200 miles on the oil. No oil use during this last run.
    "Aerodynamics are for people who can't build engines." -Enzo Ferrari

  7. #22
    Member Iroc2Vette's Avatar
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    Default Apex oil analysis arrived

    Here are the particulars of the report. Levels of metals and TI elements were extremely low. I received the following:

    Sandy,
    Please see the attached report for the oil sample that we received. Wear metals and titanium in particular look excellent.
    Have a great day

    Jason Rainey
    Apex Oil Lab
    3876 East Paris Ave., SE
    Suite 11
    Grand Rapids, MI 49512
    Toll Free: (844) APEX OIL
    www.apexoillab.com

    copy_q79_2013-chevrolet-corvette-z06-103920_20160113_merchant-automotive-jpg
    copy_q79_2013-chevrolet-corvette-z06-103920_20160113_merchant-automotive2-jpg
    Looks like all is well after nearly 38K miles. No worries here. I probably do a lot of shortish trips, so that's why my water dilution is a bit on the high side. Other than that, looks like the heads are holding together nicely

    I emailed Jason to find out why the TBN durability number was exactly Zero...Seemed odd to me. He wrote back stating it was probably a anomaly in the testing. The only way to tell is to do another sample. Which I won't do for a while. The main thing is the stems and guides aren't grinding themselves to pieces.
    Last edited by Iroc2Vette; 01-16-16 at 10:45 AM. Reason: Updated Info.
    "Aerodynamics are for people who can't build engines." -Enzo Ferrari

  8. #23
    Member Iroc2Vette's Avatar
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    Default Latest oil analysis report-blackstone

    Sorry it's been a while. This is my latest oil report at about 45K miles. The oil has about 8K miles of use including 5 hours of track time at NJ Motorsports Park. I now have 50K miles on the car. So far, so good. Also attached is a letter from Blackstone concerning the unusually low wear inside the engine.
    13-z06-090716-jpg re-oil-report-13-z06-090716-our-lab-number-h79615-sandy-mandel-jpg
    "Aerodynamics are for people who can't build engines." -Enzo Ferrari

  9. #24
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    From a wear metals standpoint, I'd say your engine is running well. There is no evidence of guid wear and, IMO little, chance of problems going forward..
    Last edited by Hib Halverson; 04-21-17 at 08:55 PM.

  10. #25
    Member Iroc2Vette's Avatar
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    Quote Originally Posted by Hib Halverson View Post
    From a wear metals standpoint, I'd say your engine is running well. There is no evidence of guid wear and, IMO little, chance of problems going forward..
    I really hope this is truly the case. My PT warranty ends this coming September, then I'm on my own. I feel fairly comfortable with reasonable care and use of a top quality synthetic lubricant that I can get this engine to run at least a 1/4 million miles...Might have to replace a crank damper or pulley tensioner along the way...but, I really don't expect anything major to happen at this point. If it does, may it happen before this September...
    "Aerodynamics are for people who can't build engines." -Enzo Ferrari

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