Boil pasta in water with salt until barely tender. Drain and rinse in cold water. Set aside.
Melt the butter in small sauce pan. Whisk in the flour stirring constantly. When bubbly, remove from heat.
In separate sauce pan, heat milk and evaporated milk just to a boil. Add the butter and flour mixture and whisk until smooth. Add the ground pepper and nutmeg. Heat for 3 or 4 minutes. Add the crumbled bacon and cooked, drained pasta.
Grease a 9 x 13 baking pan with cooking spray. Spread the pasta mixture evenly in the prepared pan.
Combine the 4 cheese and sprinkle over the pasta. Bake at 350° for 25 minutes. If cheese needs more browning, place under broiler for a few seconds.