1. #1
    1981CJ5's Avatar
    1981CJ5 is offline Member
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    Got an aluminum valve cover to replace the plastic stock cover. Went to install and found out that 3 of the holes are not tapped at all. The holes on the drivers side and the rear hole are just that, holes, no threads at all.

    Was thinking of using heli-coil to take care of this. Anyone ever tried using these in the engine? I figured it would save a little on the install and from everything I hear they hold well. The kit comes with the bit to drill out the holes to the appropriate size and the "coils" to insert in the holes, then any correct sized bolt can be used.

    Any thoughts?
    1981 CJ5, 258 Inline 6, Blazer blower upgrade, all the rest is stock to include the Carter BBD. Changes coming soon.......

  2. i would try and tap some threads before i resort to using heli-coils
    82 CJ5 that dont run.... and is no more.... 94 Z71

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  3. #3
    cra034's Avatar
    cra034 is offline Junior Member
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    Be very careful and use a flush tap. I just intalled my aluminum valve cover on my 86 CJ7. I attempted to drill a little deeper to get more thread. Not a good idea. There must be less then 1/16 of metal, cuz I went right into the water jacket. Ended up pulling head to machine shop to drill and install studs. Looks great though!!!!! Three weekends later:)-<.

  4. #4
    Utah_jeepster's Avatar
    Utah_jeepster is offline Moderator
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    By your description I take it that the orignal threads are "stripped"?
    If that is the case a Helo-coil kit will work just fine.
    Personaly I would recomend you use lock tight ( a thread locker type /blue) when you install the helo-coil. We use it on all our thread repairs with helo-coil's and king-sert's.
    If you need to bottom tap make sure your bottoming tap is your size and it is an "STI" style. (Standard Thread Insert) Most industrial supply shops will have them available, since I doubt home depot carries them.

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  5. #5
    Junkpile's Avatar
    Junkpile is offline Senior Member
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    Some years of 258 heads had all the holes tapped, some had holes but not tapped, some didn't even have some of the holes. Just tap the unthreaded holes with a bottoming tap the same size as the others, I think they are 1/4-20 threads. Make sure you don't get any metal shavings in the engine.
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  6. #6
    olyeller's Avatar
    olyeller is offline Member
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    i did the same install about 9 months ago on my 84 cj7. as best i remember, the holes are for locating pins molded into the plastic cover. the threaded holes should have 5/16-18unc threads. you can run a 5/16 bottom tap right into the existing non-threaded holes, without any drilling and have the correct hole i.d. for the threads. i stuffed paper towels into and around the valve springs and stems and held a strong magnet next to the holes that had to be tapped. after tapping the holes, i removed the magnet with almost all the chips and used the paper towels to wipe the remaining chips away from the holes. putting the towels inside the valve cover area before tapping the holes allows you to push everything away from the inside part of the head as you clean around the holes.

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