I have already posted one warning about not letting a junkyard (or used) engine sit for any extended time without taking it apart immediately as you get it home.

In this case it apparently had a bad water jacket o-ring and sat with water in one of the rotor chambers (for a long time).
That destroyed the front and center housings, and now, just as I was about to assemble the perfectly cleaned front rotor, I noticed that the surface (wall) the oil seals rests against are badly corroded.

Assuming the damage wasn't already done when I took it out of the car in the junkyard, letting it sit for years cost me otherwise perfectly usable center and front housings and a rotor. (The chrome surface of the rotor housing survived.)

Finn
(cleaning best rotor from my most recently running engine)