Preheat the oven to 350°F. Sift together the flour, salt, baking powder, and baking soda. In a separate bowl, cream the granulated sugar and butter, then beat in the eggs one at a time. Add the orange juice alternately with the flour mixture. Add the vanilla, orange extract, and walnuts; stir well. Pour into 3 well-greased 6x3-½-inch pans. Bake for about 40 minutes, or until a toothpick inserted in the center comes out clean. Remove from the pans and cool on wire racks. Wrap in plastic wrap and chill well before slicing.