bmwe21.net forums

Haven't been on this forum in years (last had e21 in 90's, but always a soft spot).
Ran across two factory rebuilt (new?) M20 engines. Have been in a warehouse for decades. 2.0 in box looks pretty decent.
2.3 with destroyed box has a coating of dust and surface rust on portions of block no longer with paint. Looks like roof leaked.
Any "consensus" as to whether should pull plugs, squirt in ATF or like, let soak few days and then try to turn crank or if should just take apart to begin with and not risk damage by trying to turn?
No, the belts have not been regularly serviced

Nice plans!

I'd start with pulling plugs, and color/residue differences of course are a sign. Some oil on the pistons and let them soak for 1-2 days, inspect timing belt if not too bad. Then you can place a wrench on the crank and carefully turn the engine by hand. If everything is moving and you feel confident, you can turn it on the starter for a compression test. But if you go that far it may be good to give it an oil change before operating the starter. Cheap oil is better than antique dirty stuff with unknown quality.

If the flywheel is fitted and the plugs are removed the engine should turn over by hand, yes you can try oil down the bores and see what happens but basically if it doesn't turn over easily any force will damage the rings and bores if there is any corrosion. So in my opinion if it doesn't turn over easily you'r into removing the head.

Borescope inspection cameras are now widely available, you can even buy one to plug into your Android phone although I can't vouch for their quality. this would enable you to look into the bores through the spark plug hole and even into the sump as well.

My 323i had the head removed and had sat in the car outside for 7 years, there was no corrosion in the bores and it turned over by hand, although I still haven't removed the sump to see what's down below, it will be rebuilt anyway.

Your profile doesn't state a location, I could be interested in the 2.3 engine if its for sale?

In Miami, Florida. No flywheel or starter; belt is new, but ?? years old. Will remove plugs, pour thin oil in cylinders, let sit for a week and not use anything bigger than a 3/8 ratchet to try and turn it. Someone suggested removing valve cover and pouring oil over cam and valvetrain while doing oil change suggested by Jeroen (hadn't thought about how old the oil in pan would be!) Will report. Thanks for suggestions. There were also a bunch of other parts; I'll put together a list as I dig through.