Any wisdom on Helicoiling a 308?

EngineerLecompte
EngineerLecompte Member
in HUDSON
The centermost bolt snapped off on my 308. This is the same bolt that holds the most of the Twin H throttle linkage down and I suspect someone in the distant past torqued the $hit out of it when installing the linkages. This was the only bolt out of the 21 that gave any problems. I have tried most every trick to get the bolt out and now I've drilled it to the point where any more will eat into the threads. I may have to drill it out completely and helicoil it. 

Any constructive thoughts?

Also, what grade of bolt is supposed to be used? These were grade 8, which seems like overkill, and has contributed to the current problem.

Comments

  • EngineerLecompte
    EngineerLecompte Member
    I meant to say: The centermost HEAD bolt snapped off on my 308. 
  • bob ward
    bob ward Senior Contributor
    The original bolts would have been grade 5. Grade 8 bolts may slightly benefit a 308 in that they can be safely tightened a bit more and clamp the gasket a bit tighter, but neither should they cause any problems.

    I've never been a fan of a design where the head bolts are used to attach various brackets to an engine, to me its not a good practice. Its quick and cheap for the maker but that's about all that can be said about it.
  • Ol racer
    Ol racer Senior Contributor

    FYI

    If broken down at the block suggest carefully drill down thru with a sharp 3/8 bit, then re-tap 7/16"...If hole 'elongates' slightly try Red Loctite a 7/16 Stud into the block then after sets up install a Nut torqued to 65#. If that fails, then drill & tap to 1/2" using a 1/2" bolt or Stud.. Later blocks have 1/2" Bolts anyway.

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