I remove them from all my builds. Sometimes the new seals in the timing cover actually press against the slinger and push the clearance out of the crank thrust surface on one side. We always check the crank thrust on every engine that someone else builds before and after it bolts on the dyno. Before bolting them up we have found thrust forward and the crank springs back when releasing the pressure. Each time it has been the slinger pushing against the extended seal acting like a spring shoving the crank to the back of the engine. We haven't had any leaks from tossing the slinger into the trash.