There was supposedly a guy that used water hydrolysis and ran the resultant hydrogen through a standard carburetor -- back in the 80's if I remember correctly. There were YouTube videos about him once upon a time, but I don't know if they're still up. The engine was on something like a modified dune-buggy frame as I recall.

Found him... Stanley Meyer. Thought to have been offed by petro-black ops or some such.