I've often wondered...
Could you not take two inline 4 motorcycle engines, and put them together into a car? Would that create double the HP and torque of just the one engine alone in a bike?
It would be fun to drive a car with a 12,000rpm redline, nice and smooth from essentially a small block 8 cylinder engine.
I don't think you could just take two engines and stick them together, but if you could, make one solid engine block with 8 cylinders but only have the displacement at 2.0L?