Stipped Crank bolt
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Stipped Crank bolt

  1. #1
    Member bennyb's Avatar
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    Default Stipped Crank bolt

    Crank on big blockchevy is stripped. Can this be fixed with the motor assembled? Dad is a machinist so if a jig needs to be made to keep things straight that is not a problem. Thinking either re-tapping or helicoil...

    Appreciate any thoughts.
    20'5 Advantage classic cruiser
    Go on get your ass outa here

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    Half a bubble off jrork's Avatar
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    I'm certainly no wizz kid like these other guys but I've drilled and helicoiled one with no problems whatsover. Good luck........john

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    Cantard 71hallett's Avatar
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    Quote Originally Posted by Eliminator Cruiser View Post
    Crank on big blockchevy is stripped. Can this be fixed with the motor assembled? Dad is a machinist so if a jig needs to be made to keep things straight that is not a problem. Thinking either re-tapping or helicoil...

    Appreciate any thoughts.
    Try to re-tap the threads and then install a stud...normaly just the first bit of threads get messed up....treads all gone or?
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Senior Member Boat 405's Avatar
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    Quote Originally Posted by Eliminator Cruiser View Post
    Crank on big blockchevy is stripped. Can this be fixed with the motor assembled? Dad is a machinist so if a jig needs to be made to keep things straight that is not a problem. Thinking either re-tapping or helicoil...

    Appreciate any thoughts.
    I would do some research on helicoil's, there are lots of different applications and I'm sure that you could find one that would suit this application nicely.

    check here www.mcmaster.com just to start

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    Member bennyb's Avatar
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    Did the re tap thing but they seem to give.
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  8. #6
    cfm
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    Most (not all) bolts do not go anywhere close to the end of the threads in the crank. Go measure as you may be abler to put a much longer bolt in.

    Did you happen to pull the harmonic balancer without one of those bushings that go in the snout to keep puller from damaging first couple of threads ? Would be the first, or 1 millionth to do that. Doh !

  9. #7
    Engine junkie
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    Been there done that, Helicoil works like a charm!

    A small jig would be great to keep things straight, an aluminum collar that slides over the crank snout would suffice. I have had to free hand drill these for others also, it works just be diligent about keeping it as straight as you can.
    While it is a viable idea, I would be careful trying to grab the last few threads in the bottom of the crank to anchor the balancer. You need a minimum of 1/2" of usable thread to torque and hold the bolt properly, the thought of having a balancer come flying off in a boat scares the hell out of me.
    Life's journey is not to arrive at the grave safely in well preserved body, but rather to skid in sideways, totally worn out, shouting"....holy shit.... what a ride!"

  10. #8
    Member bennyb's Avatar
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    We did the longer bolt idea today and decided we didn't like the way it felt.
    I don't care for helicoils, I know a lot of people use them but I just feel safer tapping a new size.
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  11. #9
    I'm No Expert Shaun's Avatar
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    Quote Originally Posted by cfm View Post
    Did you happen to pull the harmonic balancer without one of those bushings that go in the snout to keep puller from damaging first couple of threads ? Would be the first, or 1 millionth to do that. Doh !
    My buddy did that on his 350, except he didnt put a bolt in the crank at all, and drove the puller right down into the crank. Lucky for him he realized after he killed the first couple threads so he just re-tapped with the same size and had plenty of threads left further down.

    I like the idea of re-tapping bigger, with the crank i cant see a reason why not too, seams like there is plenty of material?

  12. #10
    Member bennyb's Avatar
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    Quote Originally Posted by cfm View Post
    Did you happen to pull the harmonic balancer without one of those bushings that go in the snout to keep puller from damaging first couple of threads ? Would be the first, or 1 millionth to do that. Doh !
    No but if I did I wouldn't admit it
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  13. #11
    steelcomp was here
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    I'd just go to the next size. Nothing wrong with that.
    If God is your co-pilot, change seats!
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    steelcomp was here
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    Quote Originally Posted by Shaun View Post
    My buddy did that on his 350, except he didnt put a bolt in the crank at all, and drove the puller right down into the crank. Lucky for him he realized after he killed the first couple threads so he just re-tapped with the same size and had plenty of threads left further down.

    I like the idea of re-tapping bigger, with the crank i cant see a reason why not too, seams like there is plenty of material?
    I think in '69, the 300hp Taniwanda 350 came with a pressed on balancer. The crank wasn't even drilled for a bolt. One of GM's shining moments of engineering.
    If God is your co-pilot, change seats!
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    Senior Member Bigblockbill's Avatar
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    Might look at using a Keensert over a helicoil. I repaired a crank with a keensert and ran that motor for 5 years before I sold the boat and never had a problem.
    24' Eliminator Fundeck

  16. #14
    Member bennyb's Avatar
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    Bigblockbill, did you use the thin wall or thick wall?
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