Abstract: A compression engine braking system for an engine is disclosed having two exhaust valves 26a and 26b per cylinder, a crosshead 28 in contact with both exhaust valves 26a and 26b and a rocker 30 arranged in the drive train between an exhaust cam and the crosshead 28. One end of the rocker 30 acts on a point on the crosshead 28 lying between the exhaust valves 26a and 26b and the other end of the rocker is arranged to follow the surface of the exhaust cam. The braking system comprises a hydraulic primary piston 12 arranged in a hydraulic circuit 16 with a secondary cylinder 14 acting on one of the exhaust valves 26a. The primary cylinder is biased by a spring away from said other end of the rocker 30 when the compression brake is inactive and is biased by the pressure in the hydraulic circuit 16 to move with the other end of the rocker 30 when the compression brake is active. In the invention, a spring biased lash adjuster is arranged between the rocker 30 and the crosshead 28.