[s-cars] Spark Plugs

[j.n.tilden@comcast.net]

Many time I have seen the reference to torquing spark plugs to some value (22 ft-lbs etc.)
I recall sometime deep in the dark past of my history as a young mechanic, reading some literature about spark plugs and saw a recommendation for tightening spark plugs.
Tighten the plugs hand tight into chased and cleaned openings and then tighten an additional 90 degree of rotation.

The key here is clean and chased threads. I also have always (here it comes) used anti-seize in all applications as a lubricant and an aid to removing the plugs in the future. I have an extensive and successful history of never loosing a spark plug, nor stripping out a spark plug hole in un-countless applications of air and water cooled aluminum cylinder heads! So lesson here is:
1. Get a spark plug thread chasing tool! ( sort of a dull Tap with a long guide portion, Sears as 'em)
2. Use it every time!
3. Clean out the residue after using it, I use compressed air.
4. Apply an eviromentally approved (lead free) anti-seize compound every time!
5. Finger tight, plus 90 degrees of rotation!

The key here is the spark plug washer is a crush washer. Use a new washer every time and success is assured! Don't use your old plugs over again they are too cheap to take a chance on scewing up your head!

The most important part of the heat tranfer path of the spark plug is the path from the body of the spark plug to the cylinders head. If this interface is not clean, or the mate betweeen the cylinder head and the spark plug body are imperfect then the heat range for your spark plug is all messed up. If this interface is not as designed then your plugs will run too hot. Too hot a plug in a high perforance engine is an invitation to disaster! 

Soap Box OFF!

John

1995.5 S6 Avant
(many aircooled/watercooled german automobiles in my past)