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Thread: Machining Crank

  1. #1
    Join Date
    Mar 2020
    Posts
    2

    Machining Crank

    So I took my 1989 SC 3.8 liter forged crank to be checked by a local engine builder. It seems that all the mains journals minus the rear were .010”, the rear was .020”. The connecting rod journals were .010” as well. The machinist turned crank main and connecting rod journals to .020” undersize. Said he couldn’t find any bearings. Finally got some king bearings. So my question is, I’ve read not to turn the crank journals more that .010. Is that true? I am also assuming that the bearings he got were for a NA engine and not the SC motor. Is there a difference? What should I do?

  2. #2
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    17,683
    Extreme care and exceptional skill must be utilized when cutting the crank that much. Most crank shops will be careless with the radius on the rod journals and create a weak point there which results in a broken crankshaft later on in many many cases. There are only a handful of crank grinders in the entire country whom I would trust with this operation.

    That being said, bearings are the last of your worries. Yes, you can use the NA bearings.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  3. #3
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    17,683
    Also, I would not even recommend .010 on the rod journals unless the above mentioned skill and caution are employed.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

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