Decompression Bolt thread repair


4 replies to this topic
  • G-BRO

Posted May 14, 2015 - 08:27 PM

#1

Well I think the last time I did a valve adjustment I botched the threads on the side bolt of the decompression system.

Now oil ever so slowly seeps down the side of the head, on to the header and down to the water pump area. Any thoughts on a simple fix? I would really like to avoid taking the head off. I have a new replacement bolt in hand, but I'm suspecting that the threads in the head are messed up.

I think Loctite makes an aluminum thread repair....

Oh and it's a 01 426

Edited by G-BRO, May 14, 2015 - 08:31 PM.


  • grayracer513

Posted May 15, 2015 - 06:40 AM

#2

The bolt needs a copper washer; be sure it's there.  If the threads will hold 7 ft/lb (84 in/lb) they're OK.  It can be repaired by Heli-Coiling, but it's a PITA because of the need to break the drive tab off the coil.  A "Time-Sert" threaded insert is a better idea.



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  • G-BRO

Posted May 15, 2015 - 08:42 AM

#3

The bolt needs a copper washer; be sure it's there. If the threads will hold 7 ft/lb (84 in/lb) they're OK. It can be repaired by Heli-Coiling, but it's a PITA because of the need to break the drive tab off the coil. A "Time-Sert" threaded insert is a better idea.



The washer is there. I have a replacement in hand to go with the new bolt. Would tapping the threads to the next size be a potential bad move?

  • grayracer513

Posted May 15, 2015 - 10:06 AM

#4

Yes, because then you would need to make or have made a custom bolt for the hole, if you still have the manual decomp shaft in place.  the bolt has a cylindrical "nose" on it that runs in a groove in the shaft to retain it while allowing it to rotate.



  • G-BRO

Posted May 15, 2015 - 10:16 AM

#5

Yes, because then you would need to make or have made a custom bolt for the hole, if you still have the manual decomp shaft in place. the bolt has a cylindrical "nose" on it that runs in a groove in the shaft to retain it while allowing it to rotate.

I see your point. I'll see what I can do, thanks

Edited by G-BRO, May 15, 2015 - 10:20 AM.






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