the op said he is using 440 source head, if so, you Sir are using the wrong plug. a champion rc12yc or ngk fr5 is what I use. they are 5/8 hex for a better fit.
Yeah...that's what I was asking. I wasn't sure what head he has, what head 440 source sells. Hell...I wasn't even sure I was seeing the picture of the spark plug correctly.
