Grease and lightly flour two 9x1-1/2-inch round cake pans or grease one 13x9x2-inch baking pan. Set aside.
In a large mixing bowl, combine the flour, sugar, and baking soda. Add pineapple, oil, eggs, and vanilla. Beat with an electric mixer until combined. By hand, stir in pecans. Pour batter into prepared pan(s).
Bake in a 350 degree F oven for 25 to 30 minutes for round pans or 35 to 40 minutes for a 13x9x2-inch pan or until a wooden toothpick inserted near center comes out clean. Cool layer cakes on wire racks for 10 minutes. Remove from pans; cool thoroughly on wire racks. Or place 13x9x2-inch cake pan on a wire rack; cool thoroughly.
Prepare the frosting. Frost and fill round cake layers or frost the 13x9-inch cake. Cover and store in the refrigerator. Makes 12 to 16 servings