An engine including a block that has first and second intersecting pathways, and first and second rotors positioned within the first and second pathways, respectively. The first and second rotors are moveable within the first and second pathways, respectively, between first and second combustion positions. A first combustion chamber is formed within the first pathway between the first and second rotors when they are in the first combustion position, and a second combustion chamber is formed within the second pathway between the first and second rotors when they are in the second combustion position. The pathways and rotors are preferably torus shaped, and the rotors preferably have concave leading and trailing ends. The engine block preferably has a single intake for both of the first and second combustion chambers. Recesses are preferably formed in the block to receive seals that engage the rotors.