(By Richard Finch. From Enchanted Corvairs Newsletter - Corvairs New Mexico.)
Corvair people and other owners of cars with aluminum cylinder heads would be interested to know that piston-engine aircraft manufacturers such as Lycoming and Continental all advocate the use of graphite lubricant for spark plugs used in aluminum cylinder heads. Even the FAA recommends graphite thread lubricant to prevent galled or stripped threads in aircraft engines.
Champion Spark Plug Co. makes a liquid graphite-base spark plug thread lubricant that comes in a small bottle with an applicator brush inside that is a lot like a bottle of finger-nail polish, except the consistency of the liquid graphite is like thick paint. This spark plug thread lubricant is intended to be applied each time spark plugs are removed and installed, which is usually at about 100-hour intervals in most piston-engine aircraft. The Champion Spark Plug lubricant can be purchased at most local aircraft service centers and aircraft supply stores.
To prevent thread galling on our Corvairs' $1.50 spark plugs, dress each new spark plug on a rotary wire brush to remove the manufacturing burrs, then use the thread lubricant before putting them in the cylinder head. Even brand-new $30.00 aircraft spark plugs often have burrs on their threads. We can't expect ours to be any better.