Everything on this earth requires blood flow; it just matters on what exactly that blood consists of. For mammals and reptiles, blood is, well, blood.
Makes sense, doesn’t it? Of course it does. But for cars, blood flow consists of oil and fuel. And the way it gets transmitted is through the engine.
So consider the engine the so-called heart of it all. And here we have an old 1979 Camaro in the process of receiving a new engine, i.e. a heart transplant.