Quote Originally Posted by dudeling7 View Post
pretty sure its to do with the different size and shape of the quench pads on the two different heads. a gsr/b18c2 head will raise the compression slightly because of this characteristic.
The GSR head raises compression due to the small combustion chamber volume. The quench pads exist due to the shape of the combustion chamber and other than reducing the head plane CC area, has no bearing on CC volume.