drain water out on 331 hemi

408 swinger said
You may have to use a small punch and hammer to get through the gunk. Sometimes the build up gets hard like cement.

just be careful you don't go through the other side of the water jacket or the petcock itself.

One of the design flaws of using Petcocks is they have an inner part (red arrow) that is the stop. When open it is in there still and if clogged cant be cleaned by poking or drilling

Blue arrow shows path that coolant takes when open