Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Nice when they run well. 
Good idea on fully venting the crankcase when in operation. I hadn’t thought of it, but otherwise it’s gonna “breathe” blow-by around the main bearings.

It runs cooler, fires less often, and burns less fuel with the vent opened up.
I would like to see even a larger vent hole. It moves a similar volume of air in and out of the crank case as it does above the piston in the combustion chamber. Lower resistance to moving air = a better, cooler, and longer run!