Pre-heat the oven to 350°F.
Grease a loaf pan and coat it with flour. Line the bottom with a piece of parchment paper.
In a large bowl, whisk together the flour, sugar, cinnamon, cloves, nutmeg, baking soda, baking powder and salt.
In another large bowl, whisk together the oil, egg and pumpkin. Stir the dry ingredients into the pumpkin mixture in two batches. Fold in the walnuts.
Bake for 70 minutes, or until a toothpick inserted in the top comes out clean. Cool for 20 minutes, then turn onto a rack and cool completely.