Thanks Jerry,
Since the radiator and water pump are out of the engine at this time, do you think muriatic acid would be ok to use? That is to pour the acid or acid/water solution into the water pump opening and let it sit there? If so, what ratio and how long? This engine was from 1959 by the way so it has the larger water pump opening. I'm not certain about the radiator. I had it recored around 1985 and it was only used until around 1997. If I run water in and shake it, a bit of whitish material will come out but at this point I'm more interested in removing as much of the crud in the back of the engine as possible. Water drains out of the block well enough through the back plug opening but I'm certain as much of that junk as possible needs to come out of there.
By the way, when I got this engine the back coolant drain plug was rusted solid in the block. I tried everything to remove it...P'blaster, WD40, Liquid Wrench, etc plus heating/chilling (with ice) and heating and melting wax into the threads. Nothing would move it. So I ended up filing the front of the plug smooth, making a punch mark in the very center and drilling through it using successively larger bits. When I got close to the point where I thought it was prudent to stop so as not to threaten the threads, I took one of those small hacksaw blades and carefully and slowly made two cuts...one at about 6 o'clock and another at about 9 o'clock. With a good light I could see the top of threads on the 6 o'clock cut, so I knew roughly when to stop. Then I smacked that quarter of the circle with a metal chisel and small hammer until it broke loose. After that I tapped the remainder of the plug with the small hammer and it was easy to remove using a pair of common pliers. Then I ran a 1/4 npt tap through to clean out the threads and all is well. Without any doubt it was the most stubborn rusted in plug I've ever seen. I pass this on in case others have this same problem. Also I found Amazon a good source of brass drain screws and other brass fittings. They have some of the old type that the hardware stores and auto parts stores don't carry around here.
Jon
