This is for a 1973 25ss engine I am working for some PM. Any recommendations on cleaning the coating that builds up on the cooling system aluminum surfaces around the cylinderes and adjacent areas. I have done easy to reach areas with a fine wire wheel on a variable speed drill and plan on getting a pencil shaped wire on the drill for other harder to reach areas. But is there a better way to get at the hard to reach areas, like a liquid cleaner of some type? A friend mentioned Corrosion X spray.