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Author Topic: Helicoils in heads  (Read 1081 times)

TXL SP

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Helicoils in heads
« on: January 12, 2017, 09:51:17 AM »
I have a couple 340RS heads that have had the plugs broke off in them.. I haven't drilled into the meatrt of the head,but the plug is drilled out in one and I'm working on the other. They are the thin finned starburst heads so I can't get very rough with them.. If I can't get the remaining plug part to thread out,i was wondering how reliable helicoils are in these heads.
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    pooch

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    Re: Helicoils in heads
    « Reply #1 on: January 12, 2017, 12:08:55 PM »
    Take your time with drill bits. One size up at a time.  Use cutting oil.  There are a few machine shops with lazer removal technics also. Again, they are hard to find- take your time.
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    nobody

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    Re: Helicoils in heads
    « Reply #2 on: January 12, 2017, 01:49:39 PM »
    E-Z LOC has a threaded insert that is a full steel threaded sleeve that we have used a couple of times and been very happy with. Helicoil is not made for running the plug in and out of multiple times and will eventually come out with the plug. I am sure you will get lots of suggestions here.
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    Gilson435

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    Re: Helicoils in heads
    « Reply #3 on: January 12, 2017, 01:57:29 PM »
    I have never had a problem using Heli-coils in the sparkplug hole. I have an actual heli-coil brand sparkplug repair kit specifically for plug holes. It has saved me many times 8) I have a few of these kits for different size plugs.
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    chris r

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    Re: Helicoils in heads
    « Reply #4 on: January 12, 2017, 02:16:32 PM »
    I've used hardened inserts in things with success also. But you still have to drill out the hole for the insert for a plug sized hole, and it would require you to drill it out quite a bit larger than you might have room for, I can't say without seeing the head, but unless there's a lot of material around the plug hole, I would suspect the Aluminum's holding power would be compromised and it could pop right out under compression. I'm just pointing out things that are possibilities.

    Also, I'd be afraid of the drill being "pulled" into the hole. Even going up one size at a time there will be a chance that it will want to pull that bit in, even if it is lined up perfectly. Drill rpm and feed rate can quickly cause things to get out of hand.

    Considering rarity and value, If you have a drill press and can fixture the head in the exact position to make the hole and the drill centerlines line up perfectly, I would be hesitant to do it, unless you have a hard stop on it, can control the depth of cut, and peck away at it, about .010" per peck.

    A carbon EDM (electrical discharge machining) is the perfect machine for this. I used to run one and I've done hundreds of holes (not spark plug).  What you use is a piece of carbon with the number of threads per inch that match the thread pitch of the hole. The diameter is smaller than the size of the plug, and it goes down in the hole, the computer locates the center, and orbits around it until it's the proper diameter. The carbon along with electricity burns away the material that you want out of the hole.

    I'd at least ask around if any shops would be able to do it reasonably. I can't speak to the lazer pooch mentioned.

     :)
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    mikesskidoo

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    Re: Helicoils in heads
    « Reply #5 on: January 12, 2017, 04:28:51 PM »
    Im a ski doo guy and the early blizzard sandcast heads strip if you look at them wrong, lots of air bubbles in the castings, I have had very good success with helicoils. make sure the helicoil is below the surface the plug washer seals on and you shouldn't have any issues. I doo Loctite my coils in, using the primer first. 

    71coltrider

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    Re: Helicoils in heads
    « Reply #6 on: January 12, 2017, 08:15:54 PM »
    I have had better luck with regular helicoils than the larger inserts.  If i had a head with the plug broken off i would tig  weld a bolt into the shell of the plug to try and remove it that way first.  but if i had to drill one a press or mill would be must

    polarette

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    Re: Helicoils in heads
    « Reply #7 on: January 12, 2017, 11:17:04 PM »
     I have used HELI-COILS for a long time with great results, I would recommend installing with GREEN SLEEVE RETAIN LOCKTITE and let sit for 24 hours. then run a tap through to remove excess Loctite.or the sparkplug will seize to insert.
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    71SX440

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    Re: Helicoils in heads
    « Reply #8 on: January 13, 2017, 12:51:26 AM »
    I have used HELI-COILS for a long time with great results, I would recommend installing with GREEN SLEEVE RETAIN LOCKTITE and let sit for 24 hours. then run a tap through to remove excess Loctite.or the sparkplug will seize to insert.
         GOOD LUCK,

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    Re: Helicoils in heads
    « Reply #9 on: January 13, 2017, 05:50:46 AM »
     I would try cycling heat and quench on the heads to help in braking the two components loose
     I would try to apply heat around the head and away from the spark plug. Put a wrench on the remaining part of the spark plug.  when the aluminum starts to expand  apply a little torque on the left over spark plug . I would at all cost stay away from forcing the spark plugs and re sourting to helicoils
     Vic

    thepupstain

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    Re: Helicoils in heads
    « Reply #10 on: January 13, 2017, 11:32:32 AM »
    Im not a machinist, but agree with Vic.  One thing Ive tried, is heating the part that the broken item screws into..then cool it with something like kroil.
       It seemed like the stuff got sucked into the threads when cooled and things came apart.Maybe just coincidence but its worked a few times for me on other items.
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    Re: Helicoils in heads
    « Reply #11 on: January 13, 2017, 12:49:42 PM »
    Im not a machinist, but agree with Vic.  One thing Ive tried, is heating the part that the broken item screws into..then cool it with something like kroil.
       It seemed like the stuff got sucked into the threads when cooled and things came apart.Maybe just coincidence but its worked a few times for me on other items.

    Kroil is excellent.

    In my response I jumped straight to the last resort (23 year toolmaker, too much time with engineers  ::) idle assembly plants can cost millions so time is critical).

    I had a Ford truck with 300 six many years back with 99,000 miles and I was changing the plugs. The rear one turned about 20* and then squealed at me. I stopped and tried to go back and forth a couple times and I knew I was in trouble. So I found the middle of the possible movement and hit it with the Kroil, then tightened it back up. Drove it 60 miles to work and back the next day and when I tried to remove it the next morning it came right out.

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    WopOnTour

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    Re: Helicoils in heads
    « Reply #12 on: January 14, 2017, 03:44:14 AM »
    I prefer and use Timesert thread inserts. They are just a significantly more hardy repair than heli-coils
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    TXL SP

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    Re: Helicoils in heads
    « Reply #13 on: January 14, 2017, 09:28:33 AM »
    Thanks fellas! Many good plans of attack.. And Kroil is awesome stuff!!
    don't take yourself so seriously..no one else does!

    2muchfun

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    Re: Helicoils in heads
    « Reply #14 on: January 14, 2017, 12:39:58 PM »
    I have thrown out lots of repaired heads that didn't last. ;)  IMO if its not an ultra rare part,great another. ::)