I have a 99 civic si and my friend told me to swap the block to a b18, either a gsr or a type R. is the Si head any different than the gsr or type r head???

 

http://en.wikipedia.org/wiki/Honda_E...%28B-series%29
that might help

 

b16 and type r heads share the same pr3 casting. type r heads though have a mild p&p, and upgraded cams and valvetrain.

gsr heads are a p72 casting and have different valve entry angles, different bolt pattern for the intake manifold, and has a smaller combustion chamber for .3 more compression points.

all heads these are interchangeable with each other.