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Thread: Head Torque - Wet or Dry

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    Head Torque - Wet or Dry

    I'm sure this has been discussed previously, but is the head torque value listed in the service manual for lubricated or non-lubricated threads? I recently did the re-torque while hot procedure, and could feel a definite difference between the dry outside studs, and the studs under the rocker arm cover which were covered in oil. This made me think that I probably should have lubricated the stud threads when installing the head, since there were no instructions to "dry" the threads for the hot re-torque procedure. And wouldn't there have been at least a light coat of lubricant on the studs at the factory anyway for protection prior to install? My current thinking is that it's a wet value, but I would like to hear from those of you with experience in this matter.

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    Re: Head Torque - Wet or Dry

    Good question. I don't remember the workshop manual stating one way or the other. I know when I installed the ARP head stud kit in my TR3 engine, there were specific instructions concerning lubricant. They also mentioned that torque values would be different with dry threads, with oil, and with their special lubricant. Dry bolts would require more torque (have to overcome friction) to get the same clamping force. Just for information, ARP studs in this application do not require re-torqueing.
    Art
    '58 TR3A TS236xxL
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    Re: Head Torque - Wet or Dry

    Ditto. No specification; but I believe lightly oiled is correct.

    Personally, I would re-torque even with ARP studs, just to be on the safe side. Everything moves around just a tiny bit during a heat cycle, and the head gasket may deform just a bit more. It's not a question of which studs you use.
    Randall
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    Re: Head Torque - Wet or Dry

    Quote Originally Posted by TR3driver View Post
    ...

    Personally, I would re-torque even with ARP studs, just to be on the safe side. Everything moves around just a tiny bit during a heat cycle, and the head gasket may deform just a bit more. It's not a question of which studs you use.
    Actually, ARP does leave you with a bit of ambiguity concerning this matter. From their website...


    "Do I need to re-torque my head bolts or studs?

    If you follow the ARP installation instructions, there should be no need to do a re-torque. However, it may be necessary under certain circumstances if the gasket manufacturer’s instructions require it, particularly if a fire ring has been installed. ARP recommends not doing a re-torque on a hot engine."

    I haven't re-torqued, and the head was installed maybe 8 years ago, about 16K miles. I also have 0.085" shaved off the head, and a hotter cam. Maybe I should have. Maybe I got lucky. Is it too late??
    Art
    '58 TR3A TS236xxL
    '92 Mazda Miata -- Supercharged
    '07 Mazda RX-8
    '11 Mazda CX-7

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    Re: Head Torque - Wet or Dry

    Do you happen to remember what the ARP torque spec was for lubrication with oil and dry? It would be interesting to see how closely it coincides with the service manual. It looks like the current instructions from ARP only show one torque value of 110 ft-lbs using their special lubricant.

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    Re: Head Torque - Wet or Dry

    No, I don't. I think they gave some sort of approximate percentage of how much more it would take.
    Art
    '58 TR3A TS236xxL
    '92 Mazda Miata -- Supercharged
    '07 Mazda RX-8
    '11 Mazda CX-7

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    Re: Head Torque - Wet or Dry

    Always lubricated! Otherwise all the torque is lost against friction and does not tighten the nuts...with the added affect of putting much greater torsion load on the stud than it should receive. In torquing the heads, you are actually stretching the studs. That stretch is what keeps the head tight, as the stud acts like a very strong rubber band. If you lose the torque to friction, then the stud is not properly stretched and does not retain it’s clamping power.

    ARP usually provides a packet of specialized grease with their head studs. I have even seen some come pre-greased.
    John

    1955 TR2

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