Drain a can of crushed pineapple and chop walnuts, setting aside 1/8 C of pineapple for frosting. Grate carrots to two Cups. Sift together flour, baking powder, soda, salt and cinnamon. Add sugar, oil and eggs. Mix well. Stir in carrots, pineapple, leaving 1/8 C for frosting and 1/4 C walnuts. Pour into greased and floured 9 x 13 pan. Bake at 350 degree F 35 minutes to one hour or until top springs back when touched lightly. Let cool.
Mix cream cheese, sugar and margarine until fluffy. Add left over pineapple and walnuts and mix well. Apply to cooled cake. Consume. Yum!