When steam-bending wood for a kayak last summer, I found a cheap LP gas fish
cooker to be of great benefit. I remembered that when I recently tore down
my 2.1 for a rebuild--there aren't nearly as many places around town to get
parts "tanked" and the ones that are left are pretty expensive. Plus, you
never really know what the goons that work in those places are doing to your
parts. Or maybe you do.
Anyway, I was going to my mom's to pick up the fish cooker, and mentioned
that I needed to find some place in town that had steel washtubs. She had
one and loaned it to me. I placed it atop the cooker in a safe part of the
yard (on concrete) and set it boiling while adding lots of powdered laundry
detergent. It took over an hour to boil.

I lowered the block halves in and gave them about 20 minutes in each of four
positions. Then I put in as many grimy parts as would fit.

All came out as clean as the "pro shops" would have gotten them. There
wasn't too much water left, so I disposed of it in a five gallon bucket that
is going to recycling, and the solids in the bottom went in the trash.

I finished everything off with a blast from my pressure washer.

I'm quite happy with the results and the money I saved will buy at least a
tank of gas. My only cost was the detergent, the LP gas was traded for a
used vanagon fuel pump years ago.

Any way you look at it, you're setting a big, heavy pot of boiling water on
top of a roaring flame and having to stand near it and move things around.
Be ultra careful.

In the case of the 2.1 block, it's not too heavy and has plenty of studs to
gram to turn it. Wear gloves and an apron. I wouldn't do this to, say, a
diesel block without tying off the washtub securely so that it was not able
to fall over at all, and I would have had someone around to help me.

Jim