I found this on another posting. It includes shortening. That may make a difference. I will try it tomorrow and see.
7-UP POUND CAKE
2 Sticks Butter or Margarine
1/2 C Vegetable Shortening
2 C Sugar
3 C Flour
1 (7-ounce) Bottle 7-UP (or can of course)
1 Tsp Lemon or Vanilla Flavoring
1 Tsp Butter Flavoring
Preheat oven to 325. All ingredients should be at room temperature. Cream butter and shortening with sugar. Add eggs, one at a time, beating well after each. Add flour alternately with 7-up and flavorings. Bake in a greased tube pan at 325 for at least 1 hour.