In the stand mixer bowl, beat the sugar and oil. Add the eggs and pumpkin and mix on low until thoroughly combined.
In the other bowl, sift together the flour, baking soda, baking powder, salt, cloves, cinnamon, and nutmeg. Toss the walnuts with the flour mixture, and then fold the dry ingredients into the pumpkin mixture. Stir just until the dry ingredients are combined.
Pour batter into the prepared pans and bake until a tester comes out clean, about 70 minutes. Remove from the oven and allow to sit in the pans for about 10 minutes. Run a plastic knife around the edges of the bread to release it from the pan, and turn the loaves out onto a wire rack. Allow to cool completely. Keep loaves in the refrigerator.