Broken bolt in block. sigh

Discussion in 'Street/strip 400/430/455' started by Houndogforever, Nov 8, 2019.

  1. Houndogforever

    Houndogforever Silver Level contributor

    I see I have a broken off bolt on the front of the engine block. The block is out and bare.


    I've centered it pretty well, started at a 3/16 drill and am now at .221 dia drill. Minor diameterof a 5/16-18 thread is .250 so I'm really close and can see tops of some internal threads.


    I've drilled thru the bolt but the cast iron hole is still a blind hole. I soaked it in PB Blaster over night so it could leach in from on top of the bolt and from the bottom up.

    I heated up the block, tapped in an easy out and it won't let go.

    SO. Should I use a helicoil, or a time-sert to repair this? I'm not sure what is the better method.

    I'm open to suggestions.

    Attached Files:

  2. 12lives

    12lives Engage! - Jean-Luc Picard

    I've read this works but never seen it. You can use an acetylene torch to melt the steel bolt and blast out the remaining bolt. Just don't get the block red hot.
  3. Houndogforever

    Houndogforever Silver Level contributor

    Interesting. I'm a little afraid of blasting away the threads with the torch, but I might just give it a try. Worst case is I still have to repair it.
  4. Bens99gtp

    Bens99gtp Well-Known Member

    You can try to heat it up not crazy hot, and melt a candle, the wax will soak into the tread then try your easy out again
  5. 12lives

    12lives Engage! - Jean-Luc Picard

    Yeah, the wax is also popular
  6. B-rock

    B-rock Well-Known Member

    I see so many of these threads with broken water pump bolts. When I install mine im going to do it with studs. Also just by heating it hot and cooling several times should allow the last remaining bit of bolt to let go. It's so closo to the threads im wondering if the easy out is biting on the threads of the block;. Is the block going to be seeing a machine shop in the near future?
  7. telriv

    telriv Well-Known Member

    Looks like you could get a small center punch to go at the threads from the side & peel away the remaining bolt threads.
    BuickV8Mike and 1973gs like this.
  8. Houndogforever

    Houndogforever Silver Level contributor

    Well hell, that only took 2 hours. :confused: ended up just picking away at it. Once I finally got the first thread cleared, it got easier. And by easier I mean it was a giant pain in the butt. God I hate broken bolts and I hate cast iron and this was BOTH DAMNIT.

    I would drill a little bit, try to get a tap to grab and pop a thread out, then pick at it with an Awl. That would get me 1/4 to 1/2 turn. Repeat until I got all the way to the bottom with a bottoming tap, still straight and solid threads.
    I think I remember why I didn't do this on disassembly.
  9. Houndogforever

    Houndogforever Silver Level contributor

    I'm really hoping that once this engine gets closed up it is going to outlast me so the studs sound like a good idea, but hey, it will be revenge from the grave when one of my boys trys to replace it again. lol

    I'm just waiting for the head bolts and a couple ticky tack items. Should be heading to the machine shop within 2 weeks. I just dropped the transmission off this afternoon since my wife said it could be my Christmas present. :cool:
  10. B-rock

    B-rock Well-Known Member

    Let the machine shop deal with the broken bolt, They can do a better job at removing it then we can.
  11. Houndogforever

    Houndogforever Silver Level contributor

    I'm a better machinist anyway.
  12. Stevem

    Stevem Well-Known Member

    Get a 8" long thick shaft punch who's end just about fits the OD of the bust bolt and pound on with with big ball peen hammer.
    This will jar the threads loose and a easy out will back it out with ease!
  13. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    You drilled it too big for an easy out to work. You should have stopped at 3/16 or so. Glad you got it out though.
  14. Houndogforever

    Houndogforever Silver Level contributor

    My "buddy" insisted we open it up from 3/16 (.188) to .221. After he left, I worked on it myself and actually got it. What can I say?
    I agree tho, you need the easy out to have material to bite into without forcing the bolt out into the threads.
    Oh well, it's good now and really, only the outter thread is kinda buggered, but by the time you get 3 threads in, it is solid and doesn't wiggle so I'm happy.
  15. Houndogforever

    Houndogforever Silver Level contributor

    I've seen this method. I've used this method. I completely forgot about this method until right now. SMH
    I blame the reefer and not the age. Yeah.
  16. Schurkey

    Schurkey Silver Level contributor

    If you drill them centered and straight at the "tap drill" diameter, you can pull the threads out like picking up a Slinky using the top coil.

    Alternatively, heat the broken bolt cherry red, while not deliberately heating the casting it's stuck in. When it cools, the bolt should spin right out.

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