One thing that has been mentioned is that you cant violate he 2nd law of thermodynamics. Good.

Another thing is if you going to make any significant power, the hydrogen has to be direct injected in the combustion chamber. If you think that you can pipe it in like propane to a normally aspirated engine, you are wrong.

The hydrogen is low density at STP, its displaces most of the air(O2). Haven't looked at it closely, but I doubt you could even make lower explosive limit if you start out at STP. If you can, your 350ci engine might make 25-40 hp based off of relative density of the H2.