For only a couple dollars, you can modify the crankshaft of any four stroke and turn it into a steam engine. This should produce a tremendous amount of torque, as there is one power stroke per revolution, as opposed to one in every four.
Airgunman is an innovative guy. Appears he is on to making an inexpensive steam engine... Watch his series of videos... I can visualize a generator hooked up to his engine to produce on site power...Monte