On Tue, 04 Jan 2011 15:04:02 -0500, Jeff Thies
wrote:

I've got some kind of a cleanout plug on the 4" cast iron street
drain. This likely hasn't been open in 80 years.

I'm anticipating trouble. Any hints? PB Blaster a waste of time?

I figure that I'll need to some Scotch to get through this.

Jeff

Any good reason to remove it?
That's the first question I'd ask myself.
You might rap it a bit with hammer.
The dope is probably hard.
Just be wary of cracking the cast iron.
Same when you put a wrench on it, be aware of force put on the pipe
and other joints.
Get an opposing wrench on the fitting itself.
If the plug doesn't move rap it some more.
Have a new plug ready, dope, and a wire brush to clean the fitting
threads.

Disclaimer: I am not a professional plumber. I take no responsibility
for damage incurred by listening to anything I say.

--Vic