Combustion chamber for an internal combustion engine

In an internal combustion engine, an arrangement for providing controlled combustion in a combustion chamber thereof, comprising:

• a cylinder and piston guided in said cylinder;
• a combustion chamber delimited laterally by the cylindrical walls of said cylinder, delimited at a lower end by a face of said piston and delimited in part at an upper end by valve means for allowing the controlled admission of an air-fuel charge into said combustion chamber and subsequent exhaust of combustion gases therefrom,
• said valve means comprising co-axially aligned exhaust and intake valve mechanisms actuated by camming means,
• said piston face comprising a shallow bowl for accommodating therein the spark gap of a spark plug when the piston is at top dead center, and a plurality of arcuately shaped grooves situated at least partially about said shallow bowl.