DCzapla

Saw an intersting thread on the problem with sparkplug removal in 4.6 3v mustangs. As I understand it there is a design flaw in the heads....so has this problem been corrected in the FRPP ported and polished heads...anybody have experience with these heads? Id like to hear from you. Thanks

jackal119

Those heads have the updated 12MM spark plugs, 4.6 3v is not really the problem child which is really is the 5.4L. There is a tool for removing the damaged plugs if you do break one.

DCzapla

Thanks jackal.

Derf00

Uh, yes, it is a problem child for 05-early 08 4.6L mustang heads before they switched to the updated 12 mm heads. Plenty of threads on this forum and others about people breaking plugs even when following the TSB. 5.4L is the truck motor that also exhibits the problem in significant numbers.

The way to tell if you have the older style heads is to look at the Coils, Black is the older style, brown is the newer style. Or look for a build date after Oct/Nov 2007.

FRPP heads as well as most of the performance 4.6L heads ARE the newer design. Just be aware that you will need to buy new coils if you have black ones currently (older style) because the old coils don't fit with the new heads and spark plugs.