I helped my friend fix a Ford, and it was ugly. One plug blew out of the head completely. We had to a helicoil in a very awkward location. It appears that the metallurgy in the heads was bad. I've heard about the plugs breaking, but never experienced it firsthand.

 

changed plugs and got better mpg? i know some swear by different brands. and some swear by indexing for performance. and some just swear. i do know that different plugs and the gap can make a huge difference in performance on 2 cycle/strokes , since i have tuned a few. they're easy to tune-only 1 plug. i may try a different brand in my hhr, they don't look very difficult to change to me.after i change out that boat anchor filter housing. any (plug) recomendations?