[Christ]

It's not really the Z1 that's more efficient, it's the lean-burn capability that the Z1 has... That, and the upped compression and enhanced combustion characteristics that come from the combustion chambers' quench pads on either side... the Z1's head is the same casting as the Y8 head.

If you could use the lean-burn capability w/ any other Honda engine, especially ones designed to be more efficient than the Z1 california model (which doesn't have lean-burn), it would obviously win.