Getting new heads/ motor- Change program?

[turbosam6]

I was getting just a new shortblock, but now I'm going from ported irons to GN1's also. How much difference will there be? I mean as far as my program. I was on a pretty conservative tune. Will I need to change anything to fire this motor?

 

[bobc455]

Nah, should fire right up.

You might have to tweak some VE values because of some new (hopefully slightly improved) breathing charachteristics, but only 1 or 2 points. You also might find the new combination likes slightly different tune (richer, leaner, timing, etc.) than what you had before, so you might have to tweak some of those numbers. But nothing drastic.

-Bob C.