A variable valve mechanism of an internal combustion engine includes a plurality of swing members and a variable device that displaces a control shaft to displace a plurality of slider gears of the swing members at a time, thereby changing valve lifts of the plurality of swing members at a time by meshing of helical splines. The swing members include a first swing member for a predetermined cylinder of a plurality of cylinders and a second swing member for a cylinder other than the predetermined cylinder, and a helix angle of the helical splines varies between the first and the second swing members. The variable device displaces the control shaft to a predetermined normal position to perform a normal operation, and displaces the control shaft to a predetermined cylinder cutoff position to perform a cylinder cutoff operation in which the second swing member does not drive a valve.

Embodiments of the disclosure provide variable valve timing (VVT) mechanisms. A VVT mechanism according to the disclosure can include: a lever having a first end, a second end, and a fulcrum positioned therebetween; a length-adjustable push rod coupled to the first end of the lever and including an actuator therein; a rod valve coupled to the second end of the lever, the rod valve being configured to open and close an intake valve of an engine system based on a movement of the lever; and an engine control unit (ECU) operatively connected to the actuator of the length-adjustable push rod, wherein the ECU adjusts a length of the length-adjustable push rod based on an operating condition of the engine system. In addition or alternatively, the ECU can control an amount of cushioning fluid for the valves to affect the rate at which the intake valve opens or closes.