This is an experiment to see if piston valve compressed air engine would work well with my slave exhaust valve setup. This engine actually has a cam mounted on the crankshaft, but I have the cam lobe set at exactly top dead center of the piston so the valve will open at the same angle before top dead center as it closes after top dead center. Because of this timing, the engine has to have enough momentum to continue turning over TDC against the inlet air pressure. The next puzzle will be to figure out how to delay the valve opening until closer, or ideally at, top dead center, particularly at low RPM. My first experiment will be with a compression spring loaded, telescoping push rod. The idea is that as the cam starts pushing the rod upward, it will have push against a spring which will compress until it can overcome the air pressure against the poppet valve. The amount of delay will be determined the length and strength of spring. It will probably take a fair amount of experimenting to get the spring parameters right.