Originally posted by integra_nemesis
the stroke is slightly larger on the b18 head, and overall volume of the head is greater, if you're using a b16 bottom end, your compression would suck ballz. now if it was the other way around, b16 head on a b18 bottom end(ls/vtec) the result would be higher compression and increased HP.if you know anything about gas laws, then the words 'Volumetric Efficiency', or fitting as much as you can in a given space is good, and more in a smaller space is even better. 
What the? Stoke of the head ? look if you put a gsr head on a b16 block more compression.
the head does not change the stoke.