A camshaft assembly includes a base shaft including at least one lobe pack axially movably mounted on the base shaft, the lobe pack including a control groove therein. An actuator device includes a pin movably mounted to the actuator between a retracted position and an extended position for engaging with the control groove to cause axial movement of the lobe pack. The control groove includes a pin engagement region, a shifting region and an ejection region. The pin engagement region of the control groove has a first pair of sidewalls. The shifting region extends from the pin engagement region and has a second pair of sidewalls angled relative to the first pair of sidewalls and having a first portion with a varying groove width that varies relative to a groove width of the pin engagement region.

An engine system includes: a hydraulic valve stop mechanism configured to switch states of an intake valve and exhaust valve of a same stopped cylinder; a hydraulic pressure changing device configured to change hydraulic pressure supplied to the valve stop mechanism; and a valve control portion configured to control the hydraulic pressure changing device. When a return from a reduced-cylinder operation to an all-cylinder operation is requested, and an engine revolution is less than a reference revolution, the hydraulic pressure is changed such that opening of one of the valves of the stopped cylinder able to restart at an earlier stage is first restarted. When the return is requested, and the engine revolution is not less than the reference revolution, the hydraulic pressure is changed such that opening of the exhaust valve of the stopped cylinder is restarted before opening of the intake valve.

A combined-cycle combustion control type three-cylinder engine includes: a cylinder block; and cylinders arranged in a row in the cylinder block and consisting of first, second, and third cylinders so that four-cycle combustion is performed in two of the first, second, and third cylinders and two-cycle combustion is performed in the remaining cylinder. A crankshaft is provided in first, second, and third pistons and converting reciprocating motions of the respective first, second, and third cylinders into rotational motions. A camshaft receives a rotational force from the crankshaft to control intake and exhaust timings for each of the first, second, and third cylinders