Head bolt female threads stripped, Should I retap 8m or go up to 9m?

Discussion in '2-Stroke Engines' started by Fletch, Apr 20, 2011.

  1. Fletch

    Fletch Member

    I'm concerned about tapping 8m again. I don't know if it will hold? Should I jump up to 9m and drill the hole in the cylinder block and head wider?
     

  2. DuctTapedGoat

    DuctTapedGoat Member

    Measure twice and cut once - I'd say tap 8mm, and if it strips again, go up to 9mm.

    How did you strip it to begin with? Just swapping out heads?
     
    daveet66 likes this.
  3. Fletch

    Fletch Member

    I was looking at the Kg/lbs by mistake when I was setting the ft/lbs on my torque wrench. It ended up being like 20 ft/lbs, but all 3 of the other studs held up. The forth one didn't. Nothing worse than a preventable mistake like that!

    I don't follow you about measuring? Measure what, the depth?

    So tomorrow I've got to buy a tap/die set and some 9m all thread.

    Thanks
     
  4. DuctTapedGoat

    DuctTapedGoat Member

    I just mean you can take away from it, but you can't put it back. I'd say try to run proper ft/lbs of torque on 8mm retapped, and if they don't hold, then tap it back to 9mm.
     
  5. Fletch

    Fletch Member

    I gotcha... Do you think I should thread lock it in with something, JB Weld maybe? I already tried using some of the 4 hour version (JB Quick), and it didn't make any difference. Am I right in assuming you can't strip threads using a jam-nut when you put a stud in because it will just bottom out? I usually use between 12-14 ft/lbs on the head nuts. The studs and nuts are 8.8.
     
  6. DuctTapedGoat

    DuctTapedGoat Member

    I wouldn't use JB Weld or LockTite, as heat is used to remove something that's LockTited or JB Welded. Those head bolts will get hot enough to where it's not going to make any difference if you were to.

    I would use lockring washers and steel bolts though, there's unfortunately not much else out there to do.
     
  7. Fletch

    Fletch Member

    Thanks DuctTaped--- Just FWIW that JB Quick 4 hour stuff is ****. It wouldn't hold the stud with no heat at 12 ft/lbs. I figured the temp would make it useless too.

    After talking to some hardware stores and reading some threads, I've decided to use helicoil to re-thread the hole. Some say it is stronger than the original threads (on their engines) and they even use them to reinforce exhaust studs and stuff. I just ordered a kit which comes with 12 inserts, and the special tap. They tell you what size hole to drill which will be the most difficult part- getting it straight with no drill press, but not that big of a deal.

    I called around and odd size all-thread is not a commonly stocked item (size 9), nor are odd size taps (aside from tap and die kits). I know I could order both, or use a 9m bolt, but I'd like to save the work of drilling the head and cylinder body hole wider. The helicoil kit was $25 and I can use the stud I have.

    I tried retapping the 8 with no luck, which is kind of what I figured. I rarely have success retapping the same size hole.
     
  8. DuctTapedGoat

    DuctTapedGoat Member

    A helicoil kit will totally do it - let us know how well it works out!
     
  9. Fletch

    Fletch Member

    will do
     
  10. Ixlr8

    Ixlr8 Member

    I kept pulling head studs out on one of my very high compression motors..So I drilled and tapped 3/8 rod for it. Never a problem again. But waring going to this extreme is not for the faint of heart.
     
  11. Fletch

    Fletch Member

    Update: The helicoil worked perfectly- probably stronger than original threads.
     
  12. shell shock

    shell shock Member

    sorry for the necro, but if i might ask, which helicoil kit did you get? please post a link?
     
  13. Fletch

    Fletch Member

  14. shell shock

    shell shock Member

    this is for the 8mm bolts correct?
     
  15. Al.Fisherman

    Al.Fisherman Active Member

    Be careful....some kits use 8 x 1.0. I ran across one on my last build. Getting 8 x 1.0 all thread took some time as its not that common.
     
  16. Fletch

    Fletch Member

    yes 8mm head bolts. The helicoil is more solid than the original threads.
     
  17. shell shock

    shell shock Member

    woooo! thank you fletch! +1 internets for you!
     
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