Above a large bowl, open clams with a dull knife cutting through the muscles on either side of the clam's hinge. Open each clam using the knife to loosen the clam from its shells. Drop into the bowl in order to keep all the clam liquor. Pull away the clam's spout (or siphon) and the attached membrane and discard. If desired, chop up clam into smaller pieces and return to bowl.
In a large pot, saute bacon until fat is clear. Add onion, potato and sufficient water to boil the mixture. When potatoes are done, add clams and its nectar and set pot on a low boil for no more than 10-15 minutes. Then add evaporated milk, reheat and serve. Amounts may be varied to taste. Garnish with celery and thyme as desired.
Note: Clams are a good source of protein and contain fair amounts of calcium and iron.