To increase available space for intake ports in an internal combustion pushrod type overhead valve engine, pushrod and pushrod bores running adjacent the ports are repositioned away from the ports. New valve lifters are provided with pushrod seats which are offset in the desired direction. Further offset is also provided by boring new valve lifter bores for the new valve lifters, which valve lifter bores have longitudinal axes that are also offset in the desired direction. Rocker arms are also provided with pushrod seats being offset in the same direction and by the same magnitude as the offset pushrod seats and the valve lifters. This offsetting of the pushrods away from the adjacent ports allows additional space for increasing the size and cross-sectional area of the ports to increase the breathing and power of the engine.