Place shortening in a large bowl; Cream 1/2 minute with mixer at medium speed;
Scrape sides and bottom of bowl; cream another 1/2 minute at same speed.
Add 4 cups sugar, 1 cup at a time. After each addition, cream 1 minute at medium speed.
In separate bowl sift together 3 times flour, baking powder, salt, and 3-2/3 cups of sugar; sift last time into a clean bowl.
Add 2 cups of sifted ingredients to shortening-sugar.
Blend 1/2 minute at medium speed.
Turn mixture into dry ingredients; blend until it looks like cornmeal, be sure all ingredients are well blended.
TO STORE MIX: Measure mix into 6 equal parts; Spoon it lightly into measuring cup; Each part should be 3-1/2 cups; Place each part into a quart glass jar or zip-lock bags; Cover and store in a cool, dark place; When stored properly, mix stays fresh for up to a month; For longer shelf-life, store in the freezer.
Each cake mix serving will make the following size of cake: 1 square cake 8x8x2 inches; 2 round layer cake pans - 8 inches; 1 loaf cake - 10x6-1/2x2 inches; 1 sheet cake - 12x8x1 inches.
TO MAKE YELLOW CAKE WITH CAKE MIX: Use 3-1/2 Cup cake mix, 1 teaspoon vanilla, 2 medium eggs, and 3/4 cup milk; Place mix into a bowl; Make a well in center of mix; Add eggs, vanilla and all the milk to the mixture; Beat mixture 1 minute with electric mixer at low speed, scraping sides of bowl; Beat 2 minutes longer at same speed; Batter should be smooth and free of lumps; Pour into desired pans and bake in a 350 degree F oven for 30 - 40 minutes; Cake is done when it springs back up when pressed lightly in center.
WHITE CAKE: Use 3 medium egg whites instead of whole eggs.
SPICE CAKE: Add to the mix for cake: 1 teaspoons ground cinnamon, 1/2 teaspoon allspice, and 1/2 teaspoon cloves.
ORANGE CAKE: Add 1 teaspoon grated orange rind to mix and use 1/2 teaspoon lemon extract in place of vanilla.
CHOCOLATE CAKE: Add 2 extra tablespoons of milk; Stir liquid ingredients into mix until just blended; Add 2 squares of melted chocolate and blend into mixture; Continue mixing batter as directed.