Gentlemen-
The recent issue of Moss Motoring- an excellent publication, by the
way- contains a tech tip regarding spark plug replacement that poses a
potential hazard to many car owners, especially those with aluminum
cylinder heads.
I finds no fault with the basic recommendation that spark plug holes be
chased with a tap & cleaned before a new plug is installed. This is
sound advice for all, regardless of the type of cylinder head.
The statement recommending the use of an anti seize compound is what
concerns me. While this may be a good idea for many engines, there are
several sets of circumstances where that recommendation may cause just
the result it is aimed at preventing. I speak specifically about
aluminum heads, such as those found on TR7's & TR8's and Rover V8's. I
have no opinion regarding cast iron heads, a subject on which I have
little experience.
First, there are 2 general types of anti seize commonly available to the
hobbyist, silver, the most common, a low temp product best used for
suspension parts, & a copper colored product, usually labeled "High
Temperature". The silver, low temp product, will bond to spark plugs in
some cases, making there removal from an aluminum head almost impossible
without damaging the threads. I learned this the hard way. Should
someone else experience this situation, the only way I have found to
remove plugs without damage is to unscrew until strong resistance is
felt, reverse, spray a good lubricant such as silicon, back out some
more, reverse, spray, etc. It may take 10 minutes or more, but better
than helicoils. Remember, you should never remove spark plugs from an
aluminum cylinder head until it is cool. If you feel anti seize is
necessary for your requirements, use the high temp only, & use it very
sparingly.
The second, more general situation concerns a particular brand of spark
plugs, Champion. These plugs have a factory applied anti seize compound,
I am guessing that it is a dry film lubricant. On the old Cooper
Automotive web page, there was a tech tip in regard to this, which
pointedly suggested that you do not use any other anti seize product on
Champion Spark Plugs. In this competitive world, it is safe to assume
other spark plug manufacturers may also provide an anti seize coating.
To summarize, do not apply any anti seize to a spark plug without first
contacting the manufacturer to check for prohibitions, & never use low
temp anti seize on any spark plug, or any other threads subject to high
temperatures such as exhaust manifold bolts. It will do more harm than
good.
I am copying this e-mail to the 2 automotive lists I subscribe to, I
hope you are able to provide additional information to others who may
read & act upon the tech tip you have printed.
Jim Stuart
Montgomery Village, Md
jimbb88@erols.com
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