How does top fuel dragsters cool their engines?

They don't. Not the way you think about cooling an engine. First, they run for maybe a minute only. The 12 quart oil system absorbs a lot of heat during the run and then there is a physics thing called 'the latent heat of vaporization'. That means that any liquid absorbs a large amount of heat as it evaporates. And those things pump an enormous amount of fuel through them in a run. So the fuel itself absorbs a lot of heat. Each cylinder of the eight consumes the same amount of fuel as a gas hose at the gas station pump running wide open. Only this is nitromethane at $25 a gallon. So there are 8 hoses running full blast at $25/gal. Wow!