Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
In a large bowl, combine flour, salt, soda and baking powder. Add 1 1/2 cup sugar, 1/2 cup margarine, 2 eggs and vanilla; mix well. reserve 2/3 cup of batter for filling. Spread remaining batter in 9x13 inch pan. Bake the cake base for 15 minutes.
In a saucepan, heat corn syrup, 1 1/4 cups sugar and 1/4 cup margarine until melted and hot. Remove from heat and beat in reserved 2/3 cup of cake batter. Stir in 3 eggs and add pecans. Pour on top of cake. Return to oven and bake an additional 40 minutes.