Preheat oven to 300 degrees F (150 degrees C). Grease four 7x3 inch loaf pans. In a small bowl, stir together 1/4 cup white sugar and 1 teaspoon cinnamon. Dust pans lightly with cinnamon and sugar mixture.
In a large bowl, cream butter and 3 cups sugar. Mix in eggs, mashed bananas, sour cream, vanilla and cinnamon. Mix in salt, baking soda and flour. Stir in nuts. Divide into prepared pans.
Bake for 1 hour, until a toothpick inserted in center comes out clean.