An intake valve actuation (IVA) system for a dual fuel engine is disclosed. The IVA system is retrofittable between the dual fuel engine and a diesel fuel engine and includes a cam lobe with a cam-profile, a rocker arm, and an IVA piston. The rocker arm has a pad surface, which includes a plane that passes through a central axis of a rocker shaft. The rocker arm is operably connected with the cam lobe and intake valves. A rotational movement of the cam lobe corresponds to switch between the open and closed positions of intake valves. The IVA piston has a face portion, which selectively abuts against the pad surface, to temporarily lock the intake valves in open position. The IVA system defines a hand-off when the face portion abuts against the pad surface. The cam-profile facilitates constant velocity of the intake valves at the hand-off.