Aaaahh yes..... bolt stretch... BUT not all head
studs are the 'torque to stretch' type. Rod bolts yes...
but MG studs can be re-used. Triumph studs are a
torque to yield type and must be replaced each time.
....or do I have that bass-acwards. :-)
Paul Tegler
ptegler@cablespeed.com
www.teglerizer.com
----- Original Message -----
From: "Chris K" <ckotting@wideopenwest.com>
To: <mgs@autox.team.net>
Sent: Sunday, May 16, 2004 7:25 AM
Subject: Re: Torque Sequence
> >Date: Fri, 14 May 2004 13:38:20 -0500
> >From: "Larry Daniels" <ladaniels@sbcglobal.net>
> >Subject: Torque Sequence
> >
> >Hi gang,
> >
> >It's Friday afternoon and I'm sitting at my desk thinking about MG's
instead
> >of working. (Shhh)
> >
> >
> Good for you! Everyone needs a "brain break" now and again.
>
> >I have often wondered why the sequence for unbolting the head is the same
as
> >for bolting it down. If the idea of starting at the center and working
your
> >way out is to prevent putting unnatural stresses on the head, why
wouldn't one
> >do the exact reverse sequence when releasing the pressure on the head?
It
> >would make sense in my feeble little mind that, in either case, one would
not
> >want the ends to be tightened while the middle of the head is not. Where
am I
> >going astray here?
> >
> >
> I think because you're thinking that each nut gets tightened/loosened
> all the way in one pass. Quoting the Haynes manual for the MG Midget
> (the closest one on the shelf at the moment):
>
> "Following the sequence...tighten down the nuts >> a part of a turn at
> a time << to the torque wrench setting quoted in the Specifications."
>
> I usually tighten each nut about 5 ft./lbs at a time, and make as many
> as 9 passses or so around the tightening sequence after I've spun the
> nuts down to "finger tight". I'm a bit anal about it, but the point is
> that it's gradual, and by working repeatedly around the order, none of
> the head studs has significantly more tension on it than any of the
> others, keeping things flat as they get pulled together.
>
> >Also, I read that when retorquing the head one should -- again in
sequence --
> >loosen each nut a quarter turn and then retorque them. I'm not clear on
> >whether all of the nuts should be loosened and then all retorqued or each
> >should be loosened and then retorqued and then move on to the next nut in
> >succession.
> >
> One at a time. The previous answer about breaking the "stiction"
> between nut and washer (and nut and stud, for that matter) is correct.
> However, sometimes you will see a specification for torquing something
> down with lubricant on the threads. Here, you may have a lower torque
> setting, because you aren't fighting the friction.
>
> The really high-tech way (and more acurate/relaible) to do it is to
> measure bolt stretch, but that's even more anal than I am.
>
> > I wouldn't want to upset the MG gods by torquing my nuts wrong.
> >That's as close to an obvious joke as I will go.
> >
> >
> >
> Hoo boy. Talk about your "target rich environments". I'm not going
> there either.
>
> Chris K.
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