This was my first air engine that I decided to try a camshaft and valves rather than just the simple rotary valve on the crankshaft. Crankcase started out as 2 1/2 inch round bar. There is a air passage going through the thick walled crankcase and is oringed to the back of gas tank and on to the carb and into the engine. Gas tank was to be larger and higher but was a case of only material I had on hand. Gary
[youtube1]https://youtu.be/g3SZUgCCHmU[/youtube1]