I purchased a steel fuel line for my 1957 Cub and i thought the ferrules would already be set on the line but they came separate and need installed. The problem I am having is when I tighten it down they still leak. I am worried if I put additional force on them the threads will strip. Does anyone know the proper way to get the ferrules to tighten against the steel line without stripping out the threads in the fuel sediment assembly and carburetor?