How does convection help in cooling engine system?

How does convection help in cooling engine system?
Well... this takes me back to 1973 when I was an apprentice... OLD cars didn't have water pumps so they relied on convection to cool the water in the radiators. They had to be tall and worked on the principal that hot water rises and colder water falls. The header tank on top of the radiator was higher than the engine and as the water went around the engine it heated up, then it entered the radiator and fell to the bottom, all the time being cooled by the air passing through the radiator. As technology improved, water pumps were installed so bonnet lines could be lowered making a more streamlined shape. Look at Chitty Chitty Bang Bang compared with a porch 911 to see what I mean.