A Chevy Big Block always has a displacement of 400 cubic inches or more, small bores to enable efficient breathing, longer strokes, and an overall bigger shape. Big block engines offer more power and come in 2-bolt and 4-bolt mains. The larger strokes, smaller bores, and big valves in Chevy Big Blocks improve efficiency and displacement, especially for trucks or vehicles that require more power to run; this is why Big Block engines are the best in higher-demand situations. Chevy Big Blocks weigh more because of their size, mostly referred to as porcupines.