Originally posted by DemonSVT:
Originally posted by SVTmania:
What's the difference between the APP104 and APP764?


Heat range.

764's are the plugs you want to use.

104's are 1 step colder.



Not true.

They are both the "4" (i.e. stock, like Motorcraft "32") heat range. The only difference is that one is threaded all the way down, and one is only threaded part of the way. Same form, fit, and function as the taper seat sets the plug depth in the head, not the thread length. (IIRC, the 104 is full thread like AGSF and the 764 is part thread like the AWSF. I could pull one of each when I go to work tomorrow to be sure.) Either could be used and no difference would be noted in a Duratec.

Now, the APP103 is one heat range colder, like Motorcraft "22" heat range.