Glenn,
I know its been a while since this was posted, but I needed to talk to some
of my Mechanical engineer buddies first. There are many good reasons to use
anti-seize compounds. For example, the recent posts related to the frozen
Air Injection Manifold bolting. The anti-seize will prevent rust build up
and galling so that the bolting can be removed.
You are correct that you have to account for the added slickness from the
compound because it acts as a lubricant. To complicate the matter even
more, the brand used will have different properties that affects the
required torque values differently. If you are using Never-seize, you
should use a torque value that is approximately 80% of the specified value
[0.8 X torque value]. Using the ranges supplied by the Bentley Manual, the
low end of the range is a good choice. If you used something like
Locktite-Ni Antiseez, the value would have to be 60% of the specified value
because it is even slicker. Chesterton [industrial grade] has a compound
that doesn't affect the torque value requirements at all.
IMHO, in most applications, none of this is that critical [but I'm not a
Mechanical engineer]. The torque values given are based on a percentage of
yield. There are some bolts that are taken to near yield and should be
replace every time they are loosened [because they have already been
stretched some]. The manuals usually state that the bolts should not be
reused. Most of the general bolting is taken to just over 50% yield. Also,
like Dick T. said in an earlier response, using standard wrenches are also
usually acceptable. The lengths of the different wrench sizes are for a
reason. They are designed such that a normal man [what ever normal is] will
approximate the required torque for a standard bolt. Believe it or not, the
standard engineering term for this is "snug tight".
Conclusion, use the compound when it makes sense. If you don't mind sawing
the nuts off, or if you don't plan on taking it apart again; then its not
important.
Chris Shively
69 TR6
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net]On
Behalf Of Glenn Rattmann
Sent: Thursday, February 22, 2001 11:52 AM
To: 6pack@autox.team.net
Subject: Re: Intake and exaust manifold torques
Greetings all,
I am not understanding on the torque question, in the case where
Never-Seize (or equiv) is used. If used, on something like manifold studs,
are the specified torque numbers still correct?
When I put my manifolds on a year or so back, using a torque wrench, and
N.S. on the studs, I did have problems. On one or two of the fine-thread
studs, the nut "jumped" the threads just prior to reaching spec, and then
would not tighten to spec. I ended up having to replace the stud and try
again. These were the "bronze-looking" ones, which I assume have a softer
copper (or?) plating on them.
I assumed that what might be happening was that with lube on the threads,
the nut was actually getting tighter than it should, compared to what I was
reading on the wrench. And so, I was actually over-torquing even though
the wrench was reading "ok." If so, I guess the best answer is "don't use
N.S. on the threads?" Or is it possible I just had studs with
poor-tolerance threads? Wonder how the real engine jocks handle this....
Thanks!
Glenn 74.5 TR6 X 2
San Diego "occasional shade-tree wrencher"
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