I have a quickbread recipe that bakes properly in an 8 1/2 x 4 1/2-inch loaf pan. I’d like to scale the recipe to fit a 9 x 5-inch pan (technically a 12 x 4 1/2-inch loaf pan but the volumes are the same). The volume of the smaller pan is listed as 6 c. The volume of the larger is 8 c. I’m presuming that I would multiply the original ingredients by 1.33 and adjust the baking time as needed. Is this correct?
Leavenings don’t scale all that reliably. If I were you, I’d do two batches, making a few muffins with the leftover batter. There’s a difference in baking time/temp between a 9x5 and a 12x4.5 because of how far the center of the loaf is from the long sides of the pan. You will probably find that the baking time for the Pullman loaf is about the same as for the smaller loaf pan called for in the original recipe.