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SMF bolt size?? Sources?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Fision, Feb 20, 2021.

  1. Fision

    Fision Full Access Member

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    The machine shop is finally ready to balance the rotating assembly for my 7.3 IDIT! But they lost the (9?) bolts and spacer for bolting the flywheel to the crank.

    Exactly what bolts do I need for a Single Mass Flywheel, and where can I get them?
    And where can I get the thin metal spacer?

    In trying to find the size/grade/etc, I’ve found two sizes: 3/8″-16 1-3/4″ (listed as for a flex plate, on one website) and 2-5/8” long (listed as for the factory DMF, on another website).

    In all the many DMF to SMF threads and Auto to 5-sp threads I don’t recall anyone saying they needed different bolts.
    But maybe I just wasn’t paying attention.

    Regardless, what bolts do I need for a SMF, and where can I get them? And the thin spacer??
    Thanks again!
     
  2. IDIoit

    IDIoit MachinistFabricator Supporting Member

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  3. Fision

    Fision Full Access Member

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    Thanks Russ!
    Do you have any of the spacers? I’m assuming I need one...
     
  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I'm not sure if you actually need that or not. It seems to me like the earlier 6.9's didn't use that and had washers on the bolts instead.
     
  5. Fision

    Fision Full Access Member

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    That’s good to know about the washers. Don’t see why that wouldn’t work.
    They’ll definitely be easier to find.
    Thanks!

    With. Russ’ bolts and some washers I should be set!

    And fwiw, according to one thread that included a pic of the bolt, the SMF bolts are 2-1/8” long (including 1-1/4” threads), at least for the Luk kit.

    So, ACCORDING TO HEARSAY GLEANED BY ME, Crank-to-flywheel/flex plate bolts are:

    3/8″-16 1-3/4″ (AT/flex plate)
    3/8″-16 2-1/8” (SMF)
    3/8″-16 2-5/8” (DMF)

    some say grade 8, others grade 12.

    feel free to sign my name on that rubber check.
     
  6. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I think this should work, but you may ask him first just to see what he says.
     
  7. Fision

    Fision Full Access Member

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    I received a reply (Quickly! Good customer service! Thanks, Bobby Godwin!) from Perfection HyTest , the manufacturer of my flywheel. It sounds like they spec the same bolt as does Luk. Here is their spec:


    3/8-16 Length 2.125” Grade 8

    THREAD LENGTH =1.28” with Loctite threadlock patch

    upload_2021-2-22_14-36-13.jpeg
     
  8. typ4

    typ4 Supporting Member Supporting Member

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    I ended up buying bolts from A supplier that used to service Luke when they were using USA bolts the caveat is they have a 5/8 head instead of 9/16.
    Pretty sure I made a post on oil burners about the bolts I sourced
    and I don't think the single Mass uses the spacer ring or any washers. FYI they are torqued to 47 foot pounds

    IMG_20210201_141824079.jpg
     
    Scotty4 likes this.
  9. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    You did. That's where I saw it and then placed my order for two sets.

    That's how I remember all of the IDI flywheel/flexplate bolts.
     

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