A new and improved combustion chamber and cooling system for a fastener-driving tool wherein a new and improved tangentially oriented, vortex induced fuel-injection system is operatively associated with the tool's combustion chamber. In addition, a new and improved trigger-controlled valve actuating system, such as, for example, a switch-operated, solenoid-actuated valve-controlling system, is incorporated within the tool so as to ensure the rapid operation of the intake and outlet valve structures. Still further, a sealed, liquid evaporative or liquid recirculating cooling system is integrally incorporated within the tool housing.