I just moved into my first house. Needless to say I had the Chevelle flatbedded from the old house to the new one, as it's still not in driveable condition.
This past summer, I worked on it a bit, and got it running. Filled the radiator with water, so if there were any leaks, I wouldn't make a mess with antifreeze. (And take the chance of the dogs licking it up.)
My old garage was heated.
We had some very cold temps last week, well below freezing. It's now warmed up above freezing.
Now in the new house, which does not have a heated garage, I notice water seepage coming down the block of the engine, possibly between the head and block, but definitely below the manifold. Doesn't look like a freeze plug popped.
Should I pop out the plugs to drain the water from the block and heads? What damage might I have done?

Poping the plugs is like opening the door after the cat went out. If it is freeze broken its broken:<(

I didn't notice the freeze plugs popped. Keep in mind that I also have not run the motor since the summer, since the weather turned cold. I checked the dipstick and the oil still looks like oil.
When I asked about popping out the plugs, I was referring to the engine and head block plugs to drain the water out of the motor and heads.
Where could the water be coming from?

if you can try and borrow a rad pres tester, maybe find out where its coming from-you could be screwed, or it could just be a headbolt leaking-either way, you want to pull a block plug (both sides) and the radiator drain-or heat the garage-plain water will rust up the cast iron block big time

Yo- just drain any water in the radiator and refill with antifreeze. Get it running for a few minutes and the antifreeze will circulate to stop any block freezing. It might be able to also give you an indication where the leak is, since it's usually green, if you use a paper towel and rub it around the suspected leak area.
It's more important at this time to get that block protected as fast as you can than worry about the leak whereever it's coming from.
Look around the temp guage boss on the cylinder heads on both sides. Could be from there. Remember, water hitting the ground may or may not be an indicator where it's actually coming from, since it could 'travel' to the easiest spot on the engine for it to drop on the floor.

Well it looks like my worst fears are true--the block is cracked. On both sides, just under the heads. It does look like a freeze plug popped just by the starter, but did not pop all the way out. Might be why the expansion did not give enough. We noticed small lines where paint appeared to be off the block (As though a screwdriver scraped against the block) and it looks like this is where the water is coming from-unless I'm just seeing things. I drained all water from the engine by removing the block plugs on the bottom of the motor, but don't even want to look at again until the spring. Nothing like wrecking a perfectly good motor to ruin my enthusiasm about the new house, knowing that I have absolutely no money to do anything about it.
Looks like the Chevelle sits for a few more years. If/when I do pull the 327 out, the car is getting a big block. I just hope I can sell enough of the parts to fund the change.
There's not enough expletives in my vocabulary to voice my feelings.