Aluminum heads and spark plugs

After you run that plug for a while, you’ll play hell getting it out. And you’ll be damn lucky not to pull the threads out of your aluminum heads when you try. The exposed threads themselves are nice little sharp hot spots that will heat up and glow red, helping detonation, and very likely deforming their own shape just enough to make you throw a spark plug socket through your garage wall. Please don’t do it.