A big block is a V8 engine family engineered with large bore spacing and a physically wide, heavy cast block. These dimensions allow for massive cylinder displacement, typically exceeding 400 cubic inches. Mechanics distinguish them from small blocks by their wider physical footprint, heavier weight, and distinct valve cover shapes.
Heard on the job
We had to notch the shock towers to get that big block to fit in the engine bay.
Related terms
Short block
A partially assembled engine bottom end lacking the cylinder head and oil pan.
Long block
A replacement engine assembly that includes the engine block, rotating assembly, cylinder heads, and valvetrain.
Crate engine
A fully assembled, brand-new or remanufactured engine delivered ready to install.