In large skillet, fry bacon until crisp and drain on paper towels. Crumble and set aside. Measure and reserve 4 tablespoons bacon fat. In same pan with remaining bacon fat, saute onion. When onions are transparent add potatoes and celery. Drain juice from clams into the vegetables. Add more bottled clam juice to cover the vegies and cook over medium heat until tender.
Meanwhile, in a large, heavy saucepan, melt the butter and reserved bacon fat over medium heat. Whisk in flour until smooth. Cook and stir with whisk a few minutes being careful not to brown. Whisk in cream and stir constantly until thick and smooth. Stir in vegetables and clam juice. Heat through, but do not boil.
Stir in parsley flakes, crumbled bacon and clams just before serving. If the clams cook too much they get tough. When clams are heated through, stir in vinegar, and season with salt and white pepper.