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Why my motor blew up...

Discussion in 'The Garage' started by reddog64, Oct 28, 2002.

  1. reddog64

    reddog64 1/2 ton status

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    So i felt like tearing into my 74 k5 with the blown up, fairly new sbc 400...

    I took the intake off and foound shrapnel, aluminum shrapnel...
    I then pulled the pass side head and found what was left of the number 4 piston... in 6 big chunks, the rest fell inside the block... The rod twisted to a 20 degree angle and punched a clean hole in the block... looks really cool... Looks like the piston caved in around the rod...

    the rings were wrapped around the rod.... /forums/images/graemlins/shocked.gif

    Anyone know what caused this?

    I was going down the road at 40 maybe 45 MPH...
    Tacking about 2500?
    I wasnt getting on it or anything... /forums/images/graemlins/angryfire.gif
     
  2. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    /forums/images/graemlins/frown.gif /forums/images/graemlins/confused.gif Pic's?
     
  3. TopOff

    TopOff 1/2 ton status

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    Sounds like detonation on the Piston. This caused the Piston to melt and the rod to bust through. THen the rod came out of the piston and hit the block.
    Or could be a bad pin on the piston...

    How do the other pistons look?

    Either way - it sucks. /forums/images/graemlins/frown.gif
     
  4. reddog64

    reddog64 1/2 ton status

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    the other pistons look like they only have a few miles on them.. the cylindar walls are clean and shiney, and the pistons are in good shape...

    I'm stumped...

    Working on pics should have by tonight...
     
  5. GMslave

    GMslave 1/2 ton status

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    What kind and brand pistons were they? (e.g. forged,TRW)?
     
  6. bigmack

    bigmack 1/2 ton status

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    That sucks big time, the first thing that comes to mind is a bad piston. When it was rebuilt did you have the block bored, new or resized rods, new pistons, etc ?
     
  7. Z3PR

    Z3PR Banned

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    Pic's please. I also have a 400 small block.
     
  8. reddog64

    reddog64 1/2 ton status

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    I didnt have time to get the camera today.. I'll get it tuesday and snap pics...

    There was shrapnal from aluminum piston all over the motor.. what a mess...

    I bought the motor from a guy leadfoot067 knows.. said about 10,000 miles and boarde 30 or 40 over dont remember.. I donno why it did this...

    I'm thinking a bad piston... but who knows...

    When I pull it oout and apart I'll find out what type of pistons...
     
  9. leadfoot067

    leadfoot067 1/2 ton status

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    the motor came from a good friend of mine ive known since high school....im sure it had cast pistons.as he rebuilt it for it for his 2wd truck ...
     
  10. rebelk5frk

    rebelk5frk 1/2 ton status

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    That sucks that it blew....Daddy always said if your going to break something... then break it good. /forums/images/graemlins/eek.gif
     

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