Cross threaded spark plug hole

Hienkel429
Hienkel429 Member
edited September 2014 in HUDSON
Hi all...

I just got my car and was pulling plugs to do a compression test on each cylinder.  I got to cylinder 4 and the plug had resistance coming out immediately indicating something amiss.  My suspicions were confirmed by an inspection of the plug and trying a known good plug where I got just about a 1/4 turn until resistance.  What has been your best practices in repair?  I would like to leave the head on but realize it limits my choices of helicoil, chasing, or re-tapping.  Would love to hear your thoughts.  

-Ray   

Comments

  • RL Chilton
    RL Chilton Administrator, Member
    It's unusual that the head is the one that has the problem, as it is so much harder than the threads on the plug, however, not completely unheard of.  I would simply start by chasing the head with the proper tap and seeing if that frees up the threads enough so that a plug can be inserted.  
  • charles4d
    charles4d Expert Adviser
     Sears sells a spark plug hole thread chaser about $ 8.00
  • Ol racer
    Ol racer Senior Contributor
    Its a commo9n problem especially on old aluminum heads. Try buying a sparkplug 'thread Chaser', which dont remove as much metal as a Tap. lastly, threre is a heliicoil kit available that doesnt need a Drill. The special Tap enlarges the hole as it rethreads then a tool is provided to lock the insert. If need to do this repair coat the Tapo with heavy grease thenpush oil soaked string into the hole with piston at TDC (Valves closed) then afterward most chips will stick to tap & pull out string .
  • Hienkel429
    Hienkel429 Member
    Thanks all,


    Just wanted to make sure a chaser was a good idea.  The last thing I want to do is screw something up the first time I do anything to this car.  LOL  I will pick up a chaser tomorrow along with a new plug and either do it this friday or sat.  Will let you know how it goes.  

    -Ray
  • RL Chilton
    RL Chilton Administrator, Member
    Ray-

    Is it an aluminum or iron head?
  • Hienkel429
    Hienkel429 Member
    edited September 2014
    Russell, 
     Its magnetic so iron. Here is a picture of the slightly buggered threads of spark plug. (I know its huge)

     Thanks again 
     Ray
    image
  • barrysweet52
    barrysweet52 Expert Adviser
    The grease and string is a good idea. A second person holding a vacuum cleaner will also suck out a lot of muck. Barry
  • Hienkel429
    Hienkel429 Member
    edited September 2014
    Success!  Have just run compression test on each cylinder.  Going to research what is normal before I post another question.  Thanks again

    -Ray
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