[Trapdoor2]

Be aware that this type of fitting does not seal on the threads. You must have a smooth sealing surface down at the bottom of the threads in the carburetor or the ferrule will not 'bite' and seal. Snyder's sells a rotary grinding wheel (for your dremel, I used a hurdy-gurdy hand crank drill) to grind the seat clean, esp. for rusty Zeniths. It should also work for the Tillotson if it is needed.

The brass ferrule is actually swaged to the fuel line when you torque the nut down properly...the ferrule shouldn't be removable after a proper installation.

The Tillotson has enough threads that the fitting can be safely torqued down...if they're in good shape. If you have a Zenith in good condition, I'd install the ferrule (setting the protrusion properly, etc.) using the Zenith (cast iron) and then use it on the Tillotson.