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Broken Crank Pix and Questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Chili 87 K5, Sep 4, 2000.

  1. Chili 87 K5

    Chili 87 K5 Registered Member

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    I have opened my K5's 350, and found that (as predicted), the crankshaft is broken. The wobbling crank thrashed out the #1 main bearing, leaving it in wedges and splinters.

    The bearing seat now has a definite "flaring" (a widening, or reverse-taper) around the front edge. It seems so uniform that it makes me wonder whether this shape is intentional... since I've never rebuilt one before, I have no idea.

    So I guess I have two questions:

    1) Is this the original shape of the bearing seat?

    2) If not, is there a way that I can support a new bearing without laying a weird stress/heat pattern on it?

    Thanks to all you motorheads out there!

    Brian 'Chili' G.
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I can't see the carnage er pics, or is it just me?

    [​IMG]
     
  3. lukers

    lukers Registered Member

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    I only see little red X's

    Luke
    K-5 + C-10 = K-10
     
  4. Chili 87 K5

    Chili 87 K5 Registered Member

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    Sorry: pictures not posting corectly!
     
  5. Chili 87 K5

    Chili 87 K5 Registered Member

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    Major hassle... Here's pic 1
     
  6. Chili 87 K5

    Chili 87 K5 Registered Member

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    OK, now pic #2...
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    OK on pic #2 where you have ouch written is that where the crank broke? It looks like a crack there.
    If you wiped out the bearing surface on the block (at the front) you will probably need a new block.

    [​IMG]
     
  8. Chili 87 K5

    Chili 87 K5 Registered Member

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    Roger, tRusty, that is indeed a crack in the crank... busted clean through. Most of the bearing surface seems OK, but the front 1/4" of the seat tapers out forward by about 1/16". Looks like there was extreme pressure, and the remains of the bearing are wedge-shaped in cross-section, and were extruded from the front of the block (see pic #1)

    So, I take in that the taper I'm seeing is not some Chevy ingenuity?

    BG
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    No that is not Chevy ingenuity!! LOL I would be on the lookout for a good rebuildable 4 bolt block if I were you.
    I'm actually amazed that it ran with a broken crank.[​IMG]
    Rene

    [​IMG]
     
  10. lukers

    lukers Registered Member

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    Maybe this is a stupid question here. But here goes. Could this block now be machined to accept a stock 400 crankshaft?
    Then perhaps you could set it up as a 383? If it were possible maybe it would be too expensive. Just hate to see parts go to waste.

    Luke
     
  11. realsquash

    realsquash 1/2 ton status

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  12. lukers

    lukers Registered Member

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    Since a 350 crank won't fit anymore (because of shaved metal) could you just take out enough metal for a 400 crank?
     
  13. Chili 87 K5

    Chili 87 K5 Registered Member

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    Waitaminit, all! Only the front 1/4" of the bearing seat is tapered. Is there a way to machine the damaged part of the seat to accept an insert (or filler), and then proceed as usual?
    It seems odd that there is no burr or ridge on the front of the bearing seat. I'd have thought that there'd be some kind of ridge from all that grinding, but the front of the bearing seat is smooth, both on the block and the cap.
     
  14. coopertwpk

    coopertwpk 1/2 ton status

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    You need to have the block line bored they sell oversize bearing journals also a buddy of mine showed me a trick of polishing the bearing surface with your thumb and just working the surface polishes it up .
     

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