[Mike Kelly]

Have tried them all over many years , my favourite cleaner is Citric acid, I get it in 25kg bags , much cheaper that way. Downside is the solution must be kept at a warm to hot temperature for the process to be fast and effective. If the part is very dirty or oily a bath of caustic Soda first. Have dipped engine blocks in Citric , around here in dairying country the 200 litre plastic drums are numerous and cheap, cut them in half or lengthwise .