Mushroom tappets.....the good, the bad and the ugly.

Discussion in '1st Generation Cummins' started by towcat, Mar 28, 2015.

  1. towcat

    towcat Administrator Staff Member

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    I'm doing a cam swap in a 6bt and the project got stopped in it's tracks until further inspection from the grinder. But here's my findings where the concern started.
    the left and center lifter are from one cam. the right lifter is from another.
    what makes the left one good? the wear pattern indicates the lifter is rotating properly.
    the center lifter indicates the lifter is not rotating at all.
    the right lifter shows signs of brinelling on the wear face.
    hence.....the good, the bad and the ugly.
    attention to details will make or break a long-run rebuild.
     

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  2. Clb

    Clb Another old truck Supporting Member

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    Bad orignal cam?
    Or bad tappet face?
    Interesting lifter bore wear.
     
  3. towcat

    towcat Administrator Staff Member

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    we know the left and center lifters came from a distorted block. the cam grinder is rechecking all the profiles on the lobes.
     
  4. The Warden

    The Warden MiB Impersonator Supporting Member

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    I've been helping with this project, and asked a knowledgeable person about the tappet on the right. Granted he didn't see a picture, but he said he thinks the brinelling on the wear face is from using low-emissions oil. He recommended either finding an oil that meets earlier standards, or adding a zinc additive to an oil that meets current standards.

    Hopefully that's all it is...
     
  5. The Warden

    The Warden MiB Impersonator Supporting Member

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    For anyone who's interested, I took another picture to compare the "good" tappet with the one that wasn't rotating...enjoy ;Sweet

    2015-03-30 23.06.04a.jpg

    Also, for anyone who may be interested, here's what one of the main bearings looks like after 200K miles...other than very superficial scratches, the only discoloration you can see is from residual oil ;Sweet I should note that this came from the same engine that the tappet with the pitting in towcat's original pics came out of.

    2015-03-30 21.58.14.jpg 2015-03-30 21.58.40.jpg 2015-03-30 21.58.45.jpg
     
  6. Clb

    Clb Another old truck Supporting Member

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    So how did the eng. get distorted lifter bores with a crank that clean??
     
  7. towcat

    towcat Administrator Staff Member

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    he's got his lifters confused.
    the brinnelled lifter face is part of the motor you see with the clean mains. the non-rotators are part of another motor with block distortion issues.
     
  8. The Warden

    The Warden MiB Impersonator Supporting Member

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    What he said...sorry; I should have made that more clear :oops: :sorry:
     
  9. Clb

    Clb Another old truck Supporting Member

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    THAT makes more sense!!
    Ok fine
     
  10. The Warden

    The Warden MiB Impersonator Supporting Member

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    For anyone who's interested...here are a set of brand-new tappets to compare to ;Sweet

    2015-04-03 23.24.20.jpg 2015-04-03 23.30.27.jpg
     

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