To improve engine torque and specific fuel consumption in a supermilage vehicle, we experimentally adjusted the valve lift and opening period in rocker arms, testing various follower configurations and adjust screws. Using the follower configuration in a commercially-available rocker arm, we compared 4 different levels of valve lift and opening period in the intake, and 4 different levels in the exhaust, making 16 combinations. Then, utilizing 5 kinds of modified follower configurations of the rocker arms in the intake, and 3 in the exhaust, we also compared 24 combinations (including the commercially-available follower configurations). We tested our experimental supermilage engine under full-load at 2000 to 4500rpm, simulating powering a supermilage vehicle. Results indicated that (1) with a commercially-available follower configuration of the rocker arm, specific fuel consumption decreased when setting both the open timing in the intake valve, and the close timing in the exhaust valve, at or near the top dead center (TDC), while decreasing overlap period of intake and exhaust valves. (2) With the modified follower configurations of the rocker arms, engine torque increased while specific fuel consumption decreased, when setting both the open timing in the intake valve and the close timing in the exhaust valve at or near the TDC, and the close timing in the intake valve at or near the bottom dead center (BDC), and the open timing in the exhaust valve at or near BDC, or the early opening timing in the exhaust valve.