Curt, my gin and tonic is encouraging me to reply :>)
I intended my post to focus on the real objective of determining "how tight"
the plug should be. Torque is a proxy for that clamping force and for a given
clamping force objective is a variable depending on the lubrication or not on
the threads. As you seem to agree, lubricated threads, having lower friction
between them, will turn further before stopping at a specific torque. However,
the lubricated installation will have a greater tension in the plug body, being
stretched more. Or so I submit.
Perhaps you can rationalize your view with ARP specifying lower installation
torque for their head bolts depending on whether the threads are lubricated or
not and what is the lubricant..
As for Harley specifying anti-sieze, I submit that they, like ARP, have
determined what is the desired clamping force (i.e., stress within the plug and
sealing objective) given the effect of the specified lubricant and written
their spec accordingly. Not unlike ARP and their head bolts.
To the extent that anti-sieze is in any way a lubricant is a separate question,
but I subjectively submit it has some lubricating properties above zero.
Whether it is materially different than dry is a totally different question.
Cheers (!)
Gene
----- Original Message -----
From: "Curt Hoffman" <choffman9@cinci.rr.com>
To: tigers@autox.team.net
Sent: Wednesday, April 18, 2012 11:27:13 PM
Subject: Re: [Tigers] Anti-Seize on Spark Plugs
Very common automotive blog material as to whether torque is affected by
anti-sieze. Shows up on every car list I am on. I have seen engineering
papers written on it. I personally, also being an engineer, subscribe to the
side that torque is a static measure while the lubricants tend to more
affect friction in movement. There is very little movement at the end of the
torqueing of a bolt and I find it hard to believe the antisieze would affect
the value to any great degree. Since my Harley recommends antisieze on the
plugs, and are very careful about torques for everything on the engine, I
stick with the "no real affect on torque value" position.
Curt
-----Original Message-----
From: tigers-bounces@autox.team.net [mailto:tigers-bounces@autox.team.net]
On Behalf Of genepadgett@comcast.net
Sent: Wednesday, April 18, 2012 6:14 PM
To: rfraser@bluefrog.com
Cc: Tiger's Den
Subject: Re: [Tigers] Anti-Seize on Spark Plugs
Just a caution to all about specific torque figures. The 15 - 20 ft- lb
figure in the shop manual is probably a dry torque figure. Anti-sieze on the
threads acts as a lubricant. It will result in a considerably tighter actual
clamping force (and stress on the plug threads) at a 15-20 ft-lb torque
reading than you would have at the same torque and no anti-sieze .
Gene
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