Thank you Brian,

I just removed a handfull of goo from the heater core!

I removed the heater hose at the monovalve, and the one going into the block. At first I got no flow through the heater core. So I applied constant but low pressure, let it build up, then released it. Filth, sediment, rust flakes, etc. came back toward the hose end. I did that about four or five times, until a GIANT plug of goo shot out the engine block side.

Now I can feel coolant in the hoses all around!

The air is definitely heated, but not what I'd call hot. Since it's 80 degrees in California, I'm planning to wait for a cold morning to put the thing through its paces.

Thanks for your help,

RSCarey