Now its posts like this that make me love http://hackaday.com

http://hackaday.com/2012/10/04/how-to-convert-an-internal-combustion-engine-to-run-from-steam-power/

While yes, I will be the first to admit the idea of building a functional steam engine out of a old weed wacker, 2 stroke engine, seems a little nutty, I overall like the idea compared to the price of a real steam engine. There are a couple thoughts that come to mind right off the bat.

  1. Cut off all the cooling fins. Those would only cool the steam and reduce the power of the engine. The max temp of this engine does not require the fins, as this will run way cooler than a gas engine, as there is not controlled explosion.
  2. Use proper oil, ISO 460 looks about right. Not sure if this oil would be bad for the engine type, but I think the presence of steam would be the main driving factor in oil selection. http://www.southernsteamtrains.com/notes/steam%20oil.htm
  3. Experiment with the length of the lifter arm, getting that just right is likely to make a big difference.
  4. And, As always, Be very careful if you ever mess with steam. Steam can quickly become a bomb if you don’t know what your doing. Many many people died in the steam industry prior to proper knowledge and safety standards being developed.

If this is too jerry rigged for you. You could always shell out a cool 2,400 bones for a 3 HP Engine (no boiler included.)   Going up from there things get real expensive, try 5000-45000 K for a 50+ HP engine. Yikes! http://www.enginads.com/classifieds/showcat.php/cat/7