A device and method for equalizing the pressure between work-space and crankcase in a pressurized engine, such as a Stirling engine. The device consists of a two-way valve connected between the work-space and the crankcase. The valve is connected to the work-space with a passageway including a constriction to provide an mean pressure for monitoring purposes. The valve connects the work-space and crankcase allowing the pressure to equalize when the mean pressure of the work-space exceeds the crankcase pressure by a predetermined amount.