BadFish523

But the barrel doesn't actually touch the head.

ken2736

Gotcha, thanks for the clarification!

redfishtd

Ford fix was nickel anti seize on barrel . 3 plugs designs later -- now the sp546 current plug . The carbon was also breaking plugs during installation, seafoam etc hardly touched this carbon .
Ford recommended mc carb cleaner soak on old plugs . Mine only broke where it failed to penetrate past threads . After that I cleaned all holes with carb cleaner . Carbon around tip also changed heat range of plug .
If you've ever looked at glowing carbon it's like a heat shield .
Plugs coming out squeaking means squeaking /breaking going back in .
And yes the electrolysis between alum head and steel plug is a problem .Nickel is best as ford spec'd . Just use a very thin coat and keep it off boots/porcelain . Always torque plugs in .
I would not go past 60 k on plugs. My champions are double platinum and mc are not . I saved myself from these redesigned plugs .I have a box of sp515's to get rid of .