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  1. #1
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    Default Damn It - Spark Plug Thread Repair

    ..
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    Pulled the plugs on the shovelhead the other day - the rear carb side plug was very stiff coming out. I installed these plugs last Oct (approx 9200 miles ago) and now I remember that this plug felt a little funny going in but it torqued to spec just fine and I forgot about it. I'm not sure what happened - I'm an anti-seize and torque wrench kind of guy and this was a real surprise.


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    Any ways - time for a repair. Many folks are advocates of the Heli-Coil repair for spark plug hole threads. They work OK, they are cheap and easy to install. The best thing about them is that when a customer insists on a Heli-Coil I know they will be back in the future to have the next level repair done - Big-Sert once the Heli-Coil pulls out. I use the Time-Sert repair system on my personal bike - they are more expensive, tooling is pricier, and they take more time / labor to install - but I've never had one come back.


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    Front plug carb side felt fine coming out but the threads were nasty looking about 2/3 down in the hole - so I did that one too.


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    Both primary side plug holes were fine.

    Both repaired and good to go.

    If you face this issue on your ride ask your indy or machinist if he offers Time-Sert repair. If you have the budget you should choose the Time-Sert over the Heli-Coil, especially if you plan on keeping the bike..

    My advice based on my experience - if it is useful to you use it, if not ignore it and move on..
    ..

  2. #2

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    Looks like the repair I've done on about five of the eight plug holes on my 2001 Ford 5.4. For some reason Ford forgot everything they knew about spark plug holes and decided three threads Would be enough.
    I can honestly say the repairs have held up better than the originals.
    Gotta watch torquing things with lubricants, it's not always a good idea in my opinion. Which means nothing of course.

  3. #3

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    And that 5.4 is in a van with the motor in place! It's no fun.

  4. #4

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    I've never torqued a spark plug, and never stripped one. For me, it works best doing plugs by feel. I never understood the logic behind Harley's choice to do short reach plugs on earlier bikes.

    Bill

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    Yes the short reach were a real PIA. I don't know the technical reasons for it - likely due to casting and machining process limitations..

    I ran HD early heads on this motor for several years - converted to dual plug and set up for the big bore motor. The right side plugs were long reach due to the way the dual plug conversion was performed. The left side were original short reach. Never really had issues with the short reach plugs on those heads - but the insert for the long reach plug on the front head kept cracking at the weld. Just the old standard problem of welding a relatively dense billet slug into the piss poor nasty porous HD factory castings. Never could get a reliable weld. It would last for thousands of miles and then crack - happened a couple of times and I said fuck this.

    I installed this set of S&S dual plug big bore heads about 7 years ago and never looked back They have been rock solid, no issues in almost 97K miles now. This spark plug thread problem is the only repair I've done in that time - except replace valve stem seals. And both sides are long reach...

    They need some attention now - lot of miles for a set of heads. Not passing oil past the guides and compression check still good cranking at 165#, but I can hear them. Hard to describe but at a certain wear point the valves rattle a little in the guides. I have another set on the shelf, just need to bore them for the big bore cylinders and swap them out. Leaving for a trip to Montana and Oregon next week - probably swap them when I get back. Then redo valves and guides on these and back on the shelf for next time.

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    There is a trick to turn a TIME-SERT into a pinned barrel insert. My mentor taught me in the '80s and I've used it since then with zero comebacks.

    He used a finishing nail but anything similar would work. Cut that to about 1/4" long.
    Notch the top lip of the insert to match half the cross-section of your new pin.
    Install the insert.
    Drill a hole concentric to your notch and of the same OD or tighter (test on scrap first so you KNOW the hole is right if you've not used that bit before).
    Dab some JB Weld (which acts as high-temp Loctite, or use high temp (not standard) Loctite into the hole.
    Drive the pin flush with a flat tip punch and let cure.

    Helical inserts have largely been abandoned on modern aircraft castings like gear boxes in favor of keyed inserts but live on as legacy repairs on recip engines where they were certified long before keyed inserts were common. The barrel insert is superior to the helical wire insert and the keyed insert superior to the barrel, but each has advantages.

    The helical wire insert is the thinnest and the inserts are cheap. A disadvantage in some situations is having to break off and retrieve the tang from blind holes with small inserts.
    The TIME-SERT is roughly as thin, stronger and less prone to peeling out of holes as it exerts more pressure on the tapped wall of the hole. They cost more (not enough to matter for bikers but relevant to production volume.
    Keyed inserts are more money as are most of their tooling. They are thick and sometimes unsuited for thin casting holes where the pressure they exert may crack the walls (side cases etc). I've not seen them offered for spark plugs and their tooling could be awkward in deep set plug wells, but pinning a TIME-SERT is a thin way to lock it.

    I use anti-seize on every spark plug I install and have never had a pulled thread, but I don't overtorque the plug. The objective of torquing a plug is to crush the gasket to seal the joint and provide enough friction to prevent the plug from backing out. More torque than that accomplishes nothing while anti-seize prevents galling, and excludes moisture preventing corrosion. It takes very little to coat threads and the most common error is using too much, so I don't.

  7. #7
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    Quote Originally Posted by farmall View Post
    There is a trick to turn a TIME-SERT into a pinned barrel insert. My mentor taught me in the '80s and I've used it since then with zero comebacks.

    He used a finishing nail but anything similar would work. Cut that to about 1/4" long.
    Notch the top lip of the insert to match half the cross-section of your new pin.
    Install the insert.
    Drill a hole concentric to your notch and of the same OD or tighter (test on scrap first so you KNOW the hole is right if you've not used that bit before).
    Dab some JB Weld (which acts as high-temp Loctite, or use high temp (not standard) Loctite into the hole.
    Drive the pin flush with a flat tip punch and let cure.

    Helical inserts have largely been abandoned on modern aircraft castings like gear boxes in favor of keyed inserts but live on as legacy repairs on recip engines where they were certified long before keyed inserts were common. The barrel insert is superior to the helical wire insert and the keyed insert superior to the barrel, but each has advantages.

    The helical wire insert is the thinnest and the inserts are cheap. A disadvantage in some situations is having to break off and retrieve the tang from blind holes with small inserts.
    The TIME-SERT is roughly as thin, stronger and less prone to peeling out of holes as it exerts more pressure on the tapped wall of the hole. They cost more (not enough to matter for bikers but relevant to production volume.
    Keyed inserts are more money as are most of their tooling. They are thick and sometimes unsuited for thin casting holes where the pressure they exert may crack the walls (side cases etc). I've not seen them offered for spark plugs and their tooling could be awkward in deep set plug wells, but pinning a TIME-SERT is a thin way to lock it.

    I use anti-seize on every spark plug I install and have never had a pulled thread, but I don't overtorque the plug. The objective of torquing a plug is to crush the gasket to seal the joint and provide enough friction to prevent the plug from backing out. More torque than that accomplishes nothing while anti-seize prevents galling, and excludes moisture preventing corrosion. It takes very little to coat threads and the most common error is using too much, so I don't.
    Always, always truly enjoy this gents eloquence in detailing mundane task, he's got smarts, and style.

  8. #8
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    Same gig different area ....



    Drill ...



    Counterbore ... And thread ..



    Install insert ...



    ^^ Done ^^


  9. #9
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    Yes, Virginia ... There is a 1/8" NPT Time Sert ...


    Last edited by Dragstews; 08-19-2020 at 3:16 PM.

  10. #10
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    I love Dragstews machinery porn.

    (Fapfapfapfapfapfapfapfapfapfapfapapfapfapfapfapfa pfapfapfapfapfapapfapfapfapfapfapfapfapfapfapfapap fapfapfapfapfapfapfapfapfapfapapfapfapfapfapfapfap fapfapfapfap..........)

    And of course helical wire inserts don't seal tapered threads so barrel wins again.

  11. #11
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    Sometimes ya don't have the room for a solid insert, the loose wire does have an advantage when you're dealing with that problem.



    These heads was already drilled out for 1/4 X 20 bolts ...
    The Fellow that did the job, way back when, must had been smoking the good shit cause 7 of the threads he did was like the ....






    Did take care of those ...



    Had a little help from JB Weld ...
    Could had welded all of em up, but didn't want to spend the time machining the surface back down, locating, drilling and threading ... Took the "EASY" way out ... The bolts will only be seeing 30 inch pounds of torque with using the premium James gaskets ...

  12. #12
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    I'm stealing that thread casting method.

  13. #13
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    Quote Originally Posted by farmall View Post

    I'm stealing that thread casting method.


    Last edited by Dragstews; 08-27-2020 at 3:03 PM.

  14. #14
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    You can also repair threads in plastic using the same method with a Thick CA glue. Works like a champ, I've done it any times on pastic RC car parts with stripped threads lol

    Jake

  15. #15

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    Had a little help from JB Weld ...
    Could had welded all of em up, but didn't want to spend the time machining the surface back down, locating, drilling and threading ... Took the "EASY" way out ... The bolts will only be seeing 30 inch pounds of torque with using the premium James gaskets ...[/QUOTE]

    Sooooo, if I promise not to steal the idea, how do you use jb weld to fix it? Put some in the hole and put the bolt in? How do get the bolt out?

  16. #16
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    I used the JB with the wire inserts ..

    After I pulled out the old helicoil I ran a helicoil tap back down the hole cutting some meat in order to have it straight ...
    Now the new replacement coil will be super loose in the freshly tapped hole ...
    The JB was used to fill the void and give the coil some of the footing that was lost ...

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