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Thread inserts in the Norton head

Discussion in 'Norton Commando Motorcycles (Classic)' started by comnoz, Oct 8, 2019.

  1. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    Here I have tested 4 common inserts used in the Norton head. These inserts were all 1/2 inch long. They all fit a 3/8-16 stud.

     
    worntorn, Time Warp, snail and 11 others like this.
  2. Danno

    Danno

    Joined:
    Feb 7, 2010
    I, like many others, assumed the helicoil would be first to let go, rather than last. Guess I'll keep that box of spark plug helicoils.
     
    maylar likes this.
  3. Time Warp

    Time Warp .......back to the 70's. VIP MEMBER

    Joined:
    Dec 3, 2012
    Wow.... and thanks for the kind offer the other day Jim.

    Does that mean there is only around a 3 to 5 ft/lb margin on those studs based on the test if they are meant to be torqued to 30 ft/lbs.
    Inch pounds is sounding like a much safer bet and torqued for sure.
     
    kommando likes this.
  4. Deets55

    Deets55 VIP MEMBER

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    Oct 3, 2013

    Jim,

    I’m curious to know what a standard non-repaired hole will release at. I was very surprised how little wiggle room there was in the torque range. Do you think the waisted bolts add some flexibility because of their ability to stretch a little.
    Pete
     
  5. kommando

    kommando

    Joined:
    May 7, 2005
    And if these only have a 3 to 5 ft/lb margin then the smaller original finer threaded holes must be under 30 ft/lbs, no wonder they fail.
     
  6. Time Warp

    Time Warp .......back to the 70's. VIP MEMBER

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    Dec 3, 2012
    What if...

    If the 3/8-16 helicoil went to 35 ft/lbs @ 0.500" , how much at 0.625" ?

    If you surmised that at 4.375 ft/lbs per 1/16" , at 0.625" that might add another 8.75 ft/lbs or fail at 43.75 ft/lbs which would be a much safer margin.
     
  7. jaydee75

    jaydee75

    Joined:
    Jul 2, 2012
    Thanks, a great test. What does a non-inserted stud pull at?
    Jaydee
     
  8. acadian

    acadian VIP MEMBER

    Joined:
    Mar 5, 2010
    This is fantastic, thanks Jim. I'm getting ready to repair some pulled cylinder head studs on an A65 (the through studs going into the barrel), so this is timely information.

    Do you think there would be any difference in cycling between the different inserts? Would the results be different in, say, a cast iron barrel as opposed to an alloy cylinder head?
     
  9. Onder

    Onder

    Joined:
    May 11, 2010
    How much length is available in the head all told?
     
  10. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    In a ferrous metal the solid insert would be the strongest.

    In aluminum pieces that are exposed to heat, the flexibility and coarse thread on the od makes the regular helicoil the winner.

    The main reason the Bigsert fails is the fine thread pitch on the OD.

    To beat a regular helicoil in aluminum takes a solid insert that is considerably larger and with a very coarse thread.
     
    Last edited: Oct 9, 2019
  11. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    I depends some on the head but you might get about .650 under the exhaust port before you break through.
     
  12. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    I have actually never tested one with the original thread at high temp, except on the bike where it failed when I tried to torque it to spec when it was hot.
     
  13. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    The extra length would definitely help as long as there is enough thread on the stud to take advantage of it.
     
  14. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    Prior to this test, the only tests I had done was testing regular helicoils and comparing them to the inserts that I was making from aluminum bronze.

    That is where I found I had to go really big and coarse to beat the regular old helicoil.

    Thanks to the engine builder down the street for loaning me the timesert taps, I was able to do this test.
     
  15. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    Regular helicoil inserts -not the solid ones- work fine for spark plugs. Just install them 2 or 3 threads deep to keep them from coming out.
    And then remember to go a step colder on the plug because they don't transfer heat as well.
     
  16. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    The only time I have used a waisted stud for these holes is when I was using an aluminum barrel.

    Since the cast iron barrel that the stud passes through does not expand very much, the waisted stud doesn't help.
     
  17. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    The strongest insert I have tried in aluminum was a regular 1/2-13 helicoil with an Ez-lock insert inside of it.
     
    Last edited: Oct 9, 2019
  18. ludwig

    ludwig

    Joined:
    Aug 30, 2006
    I made M14 x 2 mm bronze inserts:

    [​IMG]

    Combined with longer studs.
    You can make longer studs using a head bolt, than you already have the correct cycle tread.
    [​IMG]

    about head bolts ( off topic..): with a spacer on the centre bolt you can use 5 bolts of the same length, wich IMO is better than 4 long and 1 short.
     
    Last edited: Oct 9, 2019
    comnoz likes this.
  19. lcrken

    lcrken VIP MEMBER

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    Mar 15, 2009
    Another fascinating surprise, Jim. Thanks for posting. Definitely not what most of us would have expected. I've been using the Timeserts routinely for years on cases, cylinders, and heads on the assumption that they were stronger than helical inserts. Oh well, at least I haven't had any of them fail (yet:rolleyes:). And in some cases, there just isn't enough room for the larger diameter inserts (like with cases bored out for 920 liners). In any case, it looks like the best option is a larger OD insert, if possible, and very coarse OD threads whatever the insert size.

    Ken
     
  20. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    14mm-2 inserts is what I have in my head. But I use a 3/8-16 internal thread.
    That leaves a little material left in case I should ever pull one to go to the 16mm -2 insert.

    And yes, I use the long outer bolt in the center of my head along with a deeply finned spacer.
     
    ludwig likes this.

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