Any used engine is a crapshoot. It's possible, but not likely, that working the valves created problems, but that only happens on an engine that's on the verge of failing anyway. Unless things improve with a little driving, your only option is to do what you should have in the first place, and do a full rebuild. The only way I'll consider a used engine is a VERY low mileage one from a recent wreck. If an engine has been stored for over 6 months without some special precautions, it's probable that the cylinders will be rusty, and it will require at least a ring job to be serviceable. For engines I intend to store for longer periods, I drain the oil, and turn them upside down. The remaining oil collects around the rings and the combustion chambers, and prevents cylinder rusting. An engine that's been stored that way smokes like crazy for about a day, then clears up.
Jerry
