108 Braurtcroft Lane Snyder, New York 14226
Why not build an engine that uses no fuel at all except a 12 volt battery? Magnetism is the fuel, I guess. They're a lot of fun to build and they're cheap, too!!
Take a new or used General Motors starter solenoid and piston that gets pulled in. They become the cylinder and piston, so to speak. (Remove the yoke from the piston and peen the stub shaft tight on the piston. Remove the piston flange for best looks.) They have two separate sets of windings in them. I have found the 'hold in' windings to be the best. It is the smaller of the wires. You should have continuity between the wire and the outside of the case.
The rest is built out of scraps. Make a crankshaft to ride in ball bearings. (An old automobile water pump shaft works good.) Total stroke should be around 1' Old pulleys or sewing machine wheels have made good flywheels. I use x 3' cotter pins for the crosshead guides.
One thing to remember is the less friction, the better it will run. Make a cam to slip over the crank. It will have to be adjusted for proper timing. A set of contacts will make and break to power the solenoid. These must be insulated. Engine speed can be adjusted by varying the tension of the contacts or the voltage. Timing is very important. Some engines run better with power 'early' in the stroke and some 'late' in the stroke. All power must be off before top dead center or it will bottom out and stay there! Small Heim joints work well as a connecting rod. Old sewing machines make an excellent source for all kinds of parts flywheels, connecting rods, crankshafts, etc. With bar and flat stock, a crankshaft for two flywheels is easy to make. The next one I make will have a 'valve rocker arm' to operate the contacts.
I have made eight engines so far. Horizontal, upright and a walking beam. They all run different and they have their own personality, just like a hit and miss. They will, however, heat up in time like anything else electrical. I have also built a few with hoppers for cooling.
I have only a cheap drill press, so if you have machine tools, the sky is the limit on what you could do. They run nice, have good rhythm and won't gas you out of the house in the winter.
Good luck and have fun!!