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Thread: Con rod and head bolt torque settings.

  1. #1

    Default Con rod and head bolt torque settings.

    Does anyone know the torque settings for the head bolts and con rod end caps for a 1940 four ? It's the small con rod bolts that I don't want to over tighten and sheer off.

  2. #2
    Join Date
    Jan 2003
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    Dear Ivor, I was told 25 pound feet on the rod cap bolts by my engine builder on a Henderson KJ. I have 5/16" diameter head studs on this I-o-e engine and was told 15 pound feet by my local old bike shop. I thought this was a bit low, as the 9/16" head bolts on the VLs get pulled down to 55-60 pound feet and a 5/16" stud has half the cross section, so ended up pulling them down to 20 pound feet, then going over again after the crush rings settled down. I'd be interested in what the Indian experts have to say.

  3. #3

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    Thanks Steve, I just done the con rods at 30, and they were 5/16" (Bigger than I remember when I posted the question ) The only worry I've got there is that one of the big-ends is tight, and I'm not sure if it will just bed in ? The white metal specialists that did all the work on the crank sent the rods back to me loose but they said that they had assembled them and then taken them apart. I think the head bolts are 9/16", So I will see how 55-60 feels.

  4. #4
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    Dear Ivor, correction coming, sorry. The VL head bolts are 9/16" AF but the shanks are 7/16". The calculation about cross section is still correct, in that 5/16" studs have half the cross section of 7/16" and so should take half the torque. Big ends should not be tight on assembly. Orientation is important, and the rods and caps should all be marked to help assembly. Check with the engine builder what torque was used on the cap bolts, and if it was under 30 that might solve your tightness issue.

  5. #5

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    Thanks Steve, reducing to 20 didn't do it , so I polished of a few high spots and it's all good ! I feel 25 is a good torque by the sounds of it.

  6. #6

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    Howdy Ivor,

    Do a search here and at Caimag on Four head bolt torques. The bottom line is 55 ft lbs is far to excessive, 30 is plenty on verified flat surfaces using copper gaskets. Washer land compression and head distortion is increasingly an issue on these alloy heads now in over 75 years of use.

  7. #7
    Join Date
    Jun 2001
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    Central Illinois, USA
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    Quote Originally Posted by PRG View Post
    Howdy Ivor,

    Do a search here and at Caimag on Four head bolt torques. The bottom line is 55 ft lbs is far to excessive, 30 is plenty on verified flat surfaces using copper gaskets. Washer land compression and head distortion is increasingly an issue on these alloy heads now in over 75 years of use.
    I ain't goin' back to Caimag, Folks,..

    But nobody's torque specs have meaning if the proper torque wrench isn't applied properly.

    If you are using a 'clicker', I hope its a production line.

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  8. #8

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    Thanks for the "Heads-up" on those torque tips fellas,
    But, After about 9 years and 20k on restoring this motor that was supposed to be "Restored motor" When I bought the bike, The front engine mount fell off this-afternoon !!! So bolting the heads on is not going to be a job to be done any time soon. I honestly don't know where to go from here ?

  9. #9
    Join Date
    Jan 2003
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    England
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    Dear Ivor, you have a very desirable bike with 9 years of price inflation since you bought it, so one choice is to say 'bah humbug' and give it to Bonhams or Mecum to knock out, when you should come out whole. On the other hand, you'll miss the thrill of riding a four, and the back-and-forth camaraderie of this forum... Seasonal Greetings to all.

  10. #10
    Join Date
    Sep 2005
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    Sarasota, Florida
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    I think Steve gives very sound advice, Ivor. Give yourself a break from the project, and then go back at it with enthusiasm. 4 cylinder bikes are unique, and beautiful, and well worth doing. Don't give up on a bike you have been paying dearly for, to someone who hasn't paid your blood, sweat, and tears. I have been in your position, so I know how frustrating, and disappointing a set-back can be.
    Eric Smith
    AMCA #886

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