To get the knobs to free up you'll need to remove the top of the machine and
clean, oil and grease everything that moves. The two vertical shafts with the sliders on them to the left of the cam stack are the cam disk selector shafts. These need to be free of any old sticky oil and oiled to stay free. Lots and lots of moving metal parts in the 401. They are oil hogs.
O= oil G = grease
I recommend Tri-Flow oil for the oil places and Tri-Flow grease for the gears. Do not oil the gears, grease them.
Joe