Since the car has been giving me fits.. I went in a different direction to help clear the head. Something I've been playing with (mentally at least) is a "model" engine.. I say model that way as there are no plans.. no drawings on napkins.. just what comes out of my head and into the mill or lathe... the general direction is to do a crosshead motor. An example of a crosshead motor would be a locomotive...
So, out of a 1" plate of aluminum comes this..