In a large bowl, combine the flour, soda and salt. I a mixing bowl, beat 1-1/2 cups sugar and oil. Beat in eggs and buttermilk until combined. Stir into dry ingredients just until moistened. Fold in raisins. Combine cinnamon and remaining sugar; set aside.
Spoon half of the better into two greased 8-in x 4-in x 2-in loaf pans. Sprinkle with half of the reserved cinnamon-sugar mixture; repeat layers. Cut through batter with a knife to swirl. Bake at 350 degrees for 55-60 minutes or until a toothpick inserted near the center comes out clean. Cool in pans for 10 minutes before removing from pans to wire racks.