Remove the two 7/16" bolts that hold the valve to the motor on the passenger side by the oil filter and remove that valve. You'll probably find that the block at that location may have been sealed up in some way by a previous owner. Anyway, clean up that location. While you're there cleanup that valve and lubricate until you can move it by hand, be careful because as mentioned earlier it'll break easily. The valve I was talking about sits on top of the heater core under the dash. It's operated by sliding the stem to "heat" mounted on the dash. If working correctly you should be able to force water through either heater hose and it'll come out the other, that will drain the heater core.
Good luck, let us know how it turns out.
Hey Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
I made one for mine out of a section of an old water faucet handle. Drilled the valve stub, tapped and drilled the handle, machine screwed them together, buffed the joint, et voila! As to the learn by doing, 
there are many of us here with sore foreheads. Good talking with you from California, the salt mines await me early tomorrow so adios for now, elrey
