Busted exhaust bolt
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500, 472, 425, 368 Discussion, Busted exhaust bolt in Cadillac Engine Technical Discussion; Took off my exhaust manifolds (regrets) and managed to only break one bolt off flush. I broke two bolts, but ...
  1. #1
    ferrisworld is offline Cadillac Owners Fanatic
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    Busted exhaust bolt

    Took off my exhaust manifolds (regrets) and managed to only break one bolt off flush. I broke two bolts, but the other came right out with a pipe wrench. The one I can't get one is the front-most drivers side one. I tried drilling it all day and almost got all the way through, but then I broke off the easy-out inside of that, and the drill bits don't want to go through it. My thought is, eventually I'll pull the heads to rebuilt them anyway, so how bad would it be to just leave out that bolt? Am I likely to have a bad leak there without the bolt? I'm using manifolds from a 472.

    I guess if I take the fan shroud off, I'll be able to get a better angle on it, and I can give it another try with a 1/4 bit to really clean it out, then go in with a tap. Maybe next weekend...

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    drmenard is offline Cadillac Owners Connoisseur
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    Re: Busted exhaust bolt

    The bolts are 3/8"-16 and the tap drill for that is 5/16" drill ... If you have a broken EZ out in there the only things that will drill it out is a carbide drill. or you could melt it out with a torch..

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    ferrisworld is offline Cadillac Owners Fanatic
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    Re: Busted exhaust bolt

    Okay cool. Thanks. It kind of shattered in there, and I was able to pick out a lot of it already, but some of it is lodged in there pretty good. My hope was that with the 1/4 or 5/16 inch bit, I would be able to cut out enough of the bolt surrounding the easy out that it would just fall out. My dad has a torch I could probably use though too. Anyway, I have a 1/4 and since it's hard to make sure I'm just getting the bolt I'd rather be too small than just the right size. Right? Or is that wrong...

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Busted exhaust bolt

    Do not use the torch on the bolt if you are going to send the heads to the shop for rebuilding.Using heat will harden the stud and then you will need a carbide drill to remmove it. Have the shop remove it. A better job can be done using the proper set-up and tools.

  6. #5
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: Busted exhaust bolt

    Time for the machine shop.

    Been there.

    Gave it hell and landed up pulling the heads anyway.

    Consider it a rite of passage.

  7. #6
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Busted exhaust bolt

    That's going to be almost impossible to fix with the engine in the car. I just learned a cool trick for removing broken easy outs. I'm sure it won't work all the time, but if you still have some of the bolt left around the easy out, try drilling into what's left of the outside of the frozen bolt. The drill bit will be turning clockwise and when it makes contact with the easy out it will start turning it counter clockwise and will screw back out.........if you are a little lucky. Now this will only work on those screw type extractors and not the square type. I'll bet you used the square ones huh? I should have asked first, doh. If so, there is no easy way to get those buggers out. The head might have to go to a machine shop. It is pretty tricky using a torch to melt it out and very easy to screw it up. I know in this situation I ruin as many as I save so I would recommend a professional machine shop unless you have extra heads laying around.

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    ferrisworld is offline Cadillac Owners Fanatic
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    Re: Busted exhaust bolt

    Well, I bought 6 drill bits of various small sizes and got through it today with the help of my dad. No more easy out, but now the bits are all too dull to go through anymore of the bolt. I'm right at the end judging from how far in you can poke a wire in at each end. Can't be more than 1/8" left to go through. I did use a square type. Never again. Hopefully the spiral one I have will work when/if I get through the rest of it. I really don't want to pull the heads right now because if I do it I want to do it right which I can't really afford right now.

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Busted exhaust bolt

    You could try to re-thread it as is and use a smaller bolt in it. It won't be as strong as the original but it might hold up for a little while.

    If you invest in some left hand drill bits you can keep drilling it a little at a time until there is just a thin sheet with threads on it that may finally come spinning out. I had to buy a right angel drill for a tight job like this last year.

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    ferrisworld is offline Cadillac Owners Fanatic
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    Re: Busted exhaust bolt

    I was worried I would have to get a right angle drill, but with the engine mount bolt out and the fan off, I'm able to jack it up until the alternator hits the fender on the other side and it's just about perfect from the wheel well. I guess I can actually sharpen these cobalt bits so I'll do that, and yeah, a shorter bolt might work too, that did cross my mind.

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Busted exhaust bolt

    I don't know how to sharpen drill bits and have been leary of those sharpeners because I have never seen them work. I did ruin a complete set of left hand drill bits on my last adventure. I have never seen any hardened lefties, only the cheapos. That's good you can get good access to it with the engine jacked up. Good luck.

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    ferrisworld is offline Cadillac Owners Fanatic
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    Re: Busted exhaust bolt

    I'm just gonna sharpen them on a bench grinder. I wanna try grinding one flat and see how it works. In the past I've had bits where the tip broke, leaving essentially a flat tip in it's place, and it drilled better than when new. Wasn't much good for starting a new hole though. Thanks for the luck man.

  13. #12
    ferrisworld is offline Cadillac Owners Fanatic
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    Re: Busted exhaust bolt

    Oh yeah one thing, I read on a post somewhere someone said to use grade 8 bolts to replace the old ones, but the guy at the auto parts store said that's a bad idea because the grade 8 will more easily become brittle from the heat. Is he right?

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    jayoldschool is offline GM RWD V8 addict
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    Re: Busted exhaust bolt

    The auto parts guy is wrong.

  15. #14
    ferrisworld is offline Cadillac Owners Fanatic
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    Re: Busted exhaust bolt

    Okay. And then, any idea where I can get grade 8 ones that have the double thread for attaching the heat shield?

  16. #15
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Busted exhaust bolt

    You may find them available in some industrial supply catalogs like Grainger.

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