<VV> antiseize on plugs.

[Roger Gault]

The reason the factories don't recommend antiseize on spark plugs in
aluminum engines is that lubricating the spark plug threads reduces the
thread coefficient of friction to about half the dry case.  This means that
the tension load from tightening an antiseize coated plug is twice what it
would be for a dry plug.  The 15-20 ft-lbs that is generally recommended for
a 14mm plug in aluminum is not very much torque.  It's real easy to go way
over that.  Since most people that don't use a torque wrench will
over-tighten plugs anyway, antiseize increases the chances that some
ham-fist will pull the threads out of the head.

If you use antiseize, you should cut the torque spec in half and only use
7-10 ft-lbs.  This is a REALLY wimpy torque, so you should use a torque
wrench unless you do it every day and have a calibrated wrist.

Now, as to the other supposed reasons to not use antiseize, poor heat
conduction and poor grounding, they don't pass the goofy test.
First, keep in mind that anti-seize working has a lot more to do with
keeping corrosion from building up in the tiny gaps in the threads than it
does with having a lubricating film between the plug and the head where the
theads actually contact.

Grounding:  There are two problems with this theory.  First, since you don't
generally antiseize the washer, the plug is grounded just fine through
there.  Second, in the thread area, you've almost certainly broken through
the anti-seize at some point and established electrical contact.  Even if
you don't, the breakdown voltage of a few molecules of antiseize is
certainly WAY less than .030" of compressed air.  You are NOT going to build
up any measurable voltage between the plug and the head.  This idea is
silly.

Heat Transfer:  Again, the washer area (where most of the heat transfer
probably takes place - a good reason to use a soft washer) is unaffected.
In the thread area, you have a very small contact area, which might have a
few molecules of antiseize trapped in there.  Even if the antiseize is a
poor conductor (relative to metal) it's too thin to provide a significant
resistance to heat flow.  Most of the thread is not in contact.  In that
area, we might be fortunate enough for the antiseize to fill some of the air
gaps.  Anywhere it does, the heat conduction of the antiseize is certain to
be better that of the air that would be there if the antiseize wasn't.  So,
we should get better heat transfer with the antiseize.

Roger


----- Original Message ----- 
From: "RKHenry" <robert.henry at earthlink.net>
To: <virtualvairs at corvair.org>
Sent: Saturday, September 16, 2006 11:04 AM
Subject: RE: <VV> antiseize on plugs.


> From: Paul Abel
>
> So far, I've read that a couple of you use antiseize on the spark plugs.
> I think I recall reading in "How to Hot Rod Corvair Engines" that one
> should NOT use antiseize on spark plugs. The reason being that it
> prevents proper heat disipation from the plug to the head. Am I the only
> one who's read this? Is that not true? I use antiseize on everything
> else, but haven't used it on spark plugs.

The Corvair Service Manual specifically says to NOT use anti-seize. I
sometimes comply with that recommendation. However, I have used Champion
Spark Plug Lubricant CH2612 to good effect. This product is said to have
graphite and mica flakes in it to help heat transfer and is required on
aircraft spark plugs. Just don't get the graphite on the business end of the
plug or it'll ground the plug.

Curiously, the manual DOES specifically say to use anti-seize on engine
bolts going into aluminum. Apparently they thought for some reason that
spark plugs should be excepted. I don't know if the prohibition against
anti-seize was intended to apply to Champion CH26124 or just products like
Permatex 133K.

The only other place I've ever seen specific prohibitions against anti-seize
in a service manual is wheel lug nuts. The torque specification there is
calculated on having the lugs dry and lubricating them will cause them to be
overtorqued.

RK Henry

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