Internal combustion engine

A internal combustion engine, comprising:

• at least one cylinder provided with corresponding pistons arranged to reciprocate along a longitudinal axis of the at least one cylinder, and
• at least first and second power cams mutually opposed and connected to respective first and second rotary shafts, whereby reciprocation of the pistons results in that the pistons act on the first and second power cams to thereby impart a rotating motion to the first and second rotary shafts to drive the engine,
• wherein the engine further comprises an attachment device for connecting the first and second rotary shafts to each other so that the first and second rotary shafts rotate together, the attachment device comprising a shifting device for changing a relative angular position of the first and second rotary shafts, and
• wherein the pistons comprise at least one counter follower wheel adapted to roll on a counter cam and the cylinder has an indentation formed at opposite ends thereof so that the counter follower wheel does not collide with the cylinder;
• and
• wherein each of the indentations form a longitudinally extending open space in the cylinder wall, within which the counter follower wheel reciprocates as the pistons reciprocates along the longitudinal axis of the cylinder.