on a fuel line leading into the carbs there is a brass fitting..it screws into another brass fitting on the carb..in order to remove the fuel filters inside these carbs I have to get these two fittings apart..they are locked up like nobodys business..you cant remove the entire fitting as it twists the metal fuel line...I have to get them apart..period!... Cannot heat them as it IS a fuel line..this is on twin big block motors for a boat if ive confused anyone...any suggestions to get a couple brass fittings apart would be greatly appreciated..