How many Welch plugs?

There are a bunch; some behind the flywheel/torque converter in the bell housing. You need to find out what your problem it. When I had this problem ,it was a leaking radiator cap the was admitting fresh air in during every cool down. This produced a build up of rust in the iron block. The holes are used by the foundry to get core sand out of the castings. The name "freeze plug" is just good PR by the auto makers.