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Casting #s on flywheels?

Discussion in 'The Garage' started by mountainexplorer, May 23, 2005.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    I managed to mix up all my flywheels.

    I have a total of 5 manual flywheels. 2 are for SB400's. 3 are for 454's. I have a use for all of them, but seem to be having issues telling them apart now.

    Three of the flywheels have the casting #3973457N

    One has the #10101171 N

    And the last one is #3986394

    If anyone can decipher any of these, please let me know what's supposed to be what. Thanks.

    -------------------------------------------------------------------
    Don't read the following unless you want to be more confused-
    Of the three 3973457N flywheels, one has a 454 crank inprinted shape on it, and two have small block imprints. One of these came off a 350 motor but was a factory 454 flywheel. The other had to have been off one of the SB400's, and the other must be a 454 one for sure.

    All flywheels have the same balance weight on them (unlike automatic flexplates which I can visually see the balance weight difference).

    Each flywheel has different amounts of counter drilling on the opposing sides of the balance weight. No drilling pattern is the same.

    I have run each flywheel and know that none of them has been drilled to be zero balanced.

    I guess I should have made sure I labelled and separated them before I stacked them all in the same pile.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    If no one can help you here, might try gmpartsdirect.com (email a question) to see what part #3986394 fits. That is likely the part number too (which is not always the case) since it comes up as a flywheel, so I would suspect they or a dealer can cross reference the part number to an application.

    That was the only one of the three you posted that came up in my searches there.

    Ha! Go figure
     
  3. mountainexplorer

    mountainexplorer 1/2 ton status

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    What's weird is that two of the 3 I have are 454 ones, and one is a SB400. I wonder if they all use the same casting flywheel, but just adjust for the SB400 by drilling them a bit different.

    In any case, I still have two flywheels that I can't figure out which is which... 400 or 454.
     
  4. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    It looks like the:
    3973457N is 454
    This is a casting number, GM Number for it is: 3986391

    10101171N is 454
    this is a casting number as well. GM number for it is unlisted. That sometimes can mean the GM part number is the same, sometimes not.

    3986394 is SB400 externally balanced. That is a GM Part number.

    From those numbers, the only one that should have come on a 400 from the factory is the 3986394 one.
     
  5. HELLBENT DESIGNS

    HELLBENT DESIGNS 1/2 ton status

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    ditto on the 400 flywheel (3986394)my books for smallblocks shows that one!
     
  6. mountainexplorer

    mountainexplorer 1/2 ton status

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    Thanks guys. :)

    With that info, I can mark the 3986394 flywheel as a 400 and set it aside.

    Now, I still have one of the two 3973457N flywheels to figure out. I bought one of the flywheels as a new one from a wrecking yard for the SB400. I wonder if they just take a GM 454 flywheel and drill it to be balanced for a 400.
     

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