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Thread: Old crank shaft reuse

  1. #1
    Join Date
    Feb 2004
    Location
    Kansas City, MO
    Posts
    187

    Old crank shaft reuse

    Question I have an old 1990-91 SC automatic crank shaft that I don't know if it is reusable. How do I tell?

    thanks I also have some other engine parts for the SC heads and flywheel.

    thanks

  2. #2
    Join Date
    Oct 2018
    Location
    Nova Scotia, Canada
    Posts
    144
    A visual inspection should be your first step looking for ridges, wear, marks, ding marks, rust etc followed by checking the rod and main bearing sizes with a micrometer. If all that looks good it should be checked for cracks at a machine shop, they can also check the straightness as well. Have a look at the sealing surfaces as well front and rear.

  3. #3
    Join Date
    Feb 2004
    Location
    Kansas City, MO
    Posts
    187
    Thanks JB351, I guess, I'm asking the wrong ? What I was wanting to know is; would this old crank shaft be salable or should I just take it to the savage yard and sell it for scrap. I took it out a 90' SC block but it was not running. In fact the whole car was in a salvage yard. I used the block because I had screwed up my original block and had a guy rebuild my motor short block using the block out of the 90' Now want to get rid some of the parts that came off that motor. What I'm guessing is that if someone needed a crank then they would have to rebuild this crank. Like I said before have several motor parts will be advertising here or ebay.

    thanks

  4. #4
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    7,499
    If you just want to sanity check a crank prior to having it checked out by a $hop, free-hang it from a coat hanger or bent welding rod and tap it with a ballpeen hammer - if it rings brightly, it's solid/not cracked, could be good. If it just thuds w/a dull wump, it is most likely junk.

    Otherwise, without having a machinist familiar with how an SC crank -specifically- needs to be cut, all you can DIY without mics etc. is to visually check for obvious abnormal wear on the bearing and seal surfaces. Depending on wear and if it's been cut before, it might be worth re-using.

    AFAIK, SC cranks don't usually need much work to refresh. I think when someone goes looking for one, they've either trashed the snout, or an uninformed shop mis-cut something.
    Last edited by KMT; 09-25-2020 at 07:09 PM.

  5. #5
    Join Date
    Dec 2018
    Location
    Portland Oregon
    Posts
    22
    Quote Originally Posted by KMT View Post
    If you just want to sanity the check a crank prior to having it checked out by a $hop, free-hang it from a coat hanger or bent welding rod and tap it with a ballpeen hammer - if it rings brightly, it's solid/not cracked, could be good. If it just thuds w/a dull wump, it is most likely junk.
    .
    Sir, you just taught and an old mechanic a new (probably old) trick.

    Proof that you learn something new every day.

    BTW, Portland Engine Rebuilders there off of I-5 did my crank, rods and heads.

    All checked out perfect when plastigauged and measured.

    ~Psychic~

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