An apparatus for achieving internal EGR in a four-stroke internal combustion engine which, for each cylinder, has at least one inlet valve and at least one exhaust valve for controlling the connection between combustion chambers in the cylinder and an inlet system and exhaust system respectively. A rotary camshaft with a cam curve is designed to interact with a follower member and has a first lobe portion for generating the normal exhaust valve lift of the engine. The camshaft is provided with a second lobe portion, which has a height measurement over and above its basic curve which falls short of the measurement for normal exhaust valve clearance when driving at low load and accompanying low heat development in the engine. As a result of thermal expansion in the valve mechanism, the height measurement exceeds the measurement for normal exhaust valve clearance when driving at high load and accompanying high heat development in the engine. The second lobe portion is situated within a crankshaft angular range of about 360-480 degrees.