Camming a car means tweaking the timing and duration of the valve openings. So, to speak, alternating the lift and valve timing to get increased performance. In a 4-stroke engine, the intake or suction of fresh air-fuel mixture is called 'Lift' and the time period between the closing of the intake valve and its opening is known as 'Lift' or 'Valve Timing'. Valve timing has a great effect on engine performance, as opening and closing valves at different times can improve volumetric efficiency, or in other words the ability of the engine to suck in air and fuel and burn it completely.