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Thread: stripped spark plug holes

  1. #1
    Join Date
    Feb 2011
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    Philadelphia
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    189

    Default stripped spark plug holes

    I have a running debate on another board about the feasibility and wisdom of installing a helicoil into a spark plug hole without disassembling the engine. I know that it's a hillbilly thing to do but I am, in fact, a hillbilly. I'd like to take the temperature over here of people with more experience than just tearing down engines and re-assembling them with the occasional crisis.

    Thoughts?

  2. #2
    Join Date
    Jan 2005
    Location
    Buffalo NY
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    Default

    I have used grease on the flutes of the tap
    to catch the chips. It seems to catch them
    all. I am a believer in this, just be careful.
    A chip or two in the cylinder is not the end
    of the world. It is not like it is a 1/4-20 nut
    down in the cylinder, which I can assure you
    IS the end of the world.

    -D

  3. #3
    Join Date
    Jan 2007
    Location
    Minnesoa
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    Default

    Hi,

    Been there done that. Didn't bother with the tee-shirt. Doozer is right, just use some grease and care.

    Helicoiling a spark plug without disassembly gets done more than you might think. It might not be best practice, but it's doable for sure.
    If you think you understand what is going on, you haven't been paying attention.

  4. #4
    Join Date
    Nov 2008
    Location
    Lillooet B.C. Canada
    Posts
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    Default

    Quote Originally Posted by Doozer View Post
    I have used grease on the flutes of the tap
    to catch the chips. It seems to catch them
    all. I am a believer in this, just be careful.
    A chip or two in the cylinder is not the end
    of the world. It is not like it is a 1/4-20 nut
    down in the cylinder, which I can assure you
    IS the end of the world.

    -D
    +1 Have done this several times, if you take it in to a shop, it's what they'll likely do.......

    -Don

  5. #5
    Join Date
    May 2006
    Posts
    14,111

    Default

    X2 on post 2,

    but do multiple passes and clean and re-grease each time, if it's a cast iron head you have more concern due to the C.I. being harder and more abrasive, if it's aluminum it's going to be a long reach plug so multiple passes and cleanings, aluminum will get pumped right through but your biggest concern with it is that it sticks to an exhaust valve or seat and holds the valve open -
    keep in mind there's great tools to get the job done, heli-coil makes a special kit/tap that uses the old buggered up threads as a starting guide then engages the oversize threads as you keep going, just be sure you have the piston down and also make sure you have all the valves closed just in case as the tool has to extend way inside the head...

  6. #6
    Join Date
    Dec 2004
    Location
    East Coast, USA
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    Push an oily rag into the cylinder, do your business to the plug threads, then fish out the rag and pull it out carefully. Maybe flush out the cylinder with fluid and evacuate it with a good pump for extra measure.
    Work hard play hard

  7. #7
    Join Date
    Dec 2002
    Location
    Friesland, Netherlands
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    Default

    I'd be with Doozer on this one. I'm assuming it's an aluminium head, not on a formula one car engine. The few chips that the grease doesn't catch will probably get blown out the exhaust valve and do little harm.

    You'll probably have to drill the old thread (or its remains) out first - a nozzle to a good vacuum cleaner will help suck the chips out during drilling, then go with the tap. Keeping drill & tap on the axis of the hole could be a bit of a challenge, as you probably plan to do this with the engine still in the vehicle, yes?

    Check the diameter of the sealing gasket on the spark plug - it would be helpful if it was larger than the outer diameter of the helicoil. Loctite on the helicoil during installation might help.

    Are you using a tanged insert? This will need to be broken off and then retrieved (magnet?). It'll do more damage than a few bits of aluminium swarf...

    Ian
    All of the gear, no idea...

  8. #8
    Join Date
    May 2006
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    Quote Originally Posted by 3 Phase Lightbulb View Post
    Push an oily rag into the cylinder, do your business to the plug threads, then fish out the rag and pull it out carefully. Maybe flush out the cylinder with fluid and evacuate it with a good pump for extra measure.
    Don't do this

  9. #9
    Join Date
    Nov 2008
    Location
    Lillooet B.C. Canada
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    Quote Originally Posted by A.K. Boomer View Post
    Don't do this
    .....Although. it would be humorous watching the retrieval attempt through that little hole, on the plus side, the head would then be off for rag removal......eventually.

  10. #10
    Join Date
    Dec 2004
    Location
    East Coast, USA
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    Default

    A monkey could remove the rag...
    Work hard play hard

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