Turbo question.

[BR3W CITY]

When I think of a "larger" head I think of the chamber. Having a larger chamber on an unchanged bottom end will lower the compression ratio, but holds a larger volume of air.

If it lowers the compression lets say .5, you make less power on motor, but leave more room before detonation on boost. I think those NPI motors are like 9.2:1 and the PI heads have a 8ish cc smaller combustion chamber, which would increase your compression. It would make more power, but would be at greater risk for detonation.

Again, I don't know ford-specific stuff other than what I've seen and seen written. There are way more combos of 2v and 4v heads etc so the math I did might not even be close to what your actually working with.