The 400 Chevy is a small block engine. The 400 BIG BLOCK Chevy does not exist! 402 big block Chevy does. it seems in the early 70s Chevy put 402s in their pick ups and they had 400 badges. this...
that is basically the heap paradox. lets say you have a million grains of sand. compared to 5 grains that is a heap. if you continuously take one grain away, when does that pile of one million become...
A long block is a complete engine, the bottom part plus the heads. A big block usually refers to a large displacement North American (muscle car) engine of around 400 cu in.