You either need to drain it or fill it with antifreeze. Have you considered an expanding rubber core plug to at least fill the hole so you can get the cooling system filled with enough strait antifreeze to dilute the water in your block. Probly too hard to get access. Another alternative would be remove the water pump and either suction out the water by shoving a tube down the opening left by the water pump or filling that side the block with undiluted antifreeze through that same opening. Worst case scenario, you punch out a core plug on the side not drained. AHHHH! If you can get an oxy acetylene welding tip (not cutting tip) near your drain plug, you might be able to heat it, let it cool and see if will come out, but I think access is pretty poor there too. Lets see now, get a big wad of kids modeling clay and use it to seal up the core plug hole long enought to fill the system and run with the radiator cap off till the tstat opens. I donno thats all the ideas I can come up with short of pulling the engine and replacing all the core plugs
