Got a set of (used) shorty headers in today, there's a lot of buildup inside of them. What's the best way to clean them out (before I install them)?

They're jet-coated, but I'm not sure running water though them is the wisest idea.

 

watter prolly wouldnt do much much anyways id say carb cleaner or some gas something like that should do the trick

 

some sort of solvent, maybe brake or carb cleaner.