Re: Spark Plug Protrusion into Head?
From the picture, it sure looks like the heads weren't modified. On the plug hole on the right, you can see the complete set of threads. I'll try to take a picture of my head from the same angle and see if I can get a comparable view. BTW, my heads are stamped "425". As I said, my heads were procured from Speedway in the late nineties; do you have any idea of the age of your heads?
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