Hello bo,
The engine can be stuck from corrosion in the cylinders or other mechanical damage. Corrosion in the cylinders can be caused by coolant leakage into the cylinders. A blown head gasket, corroded head, or just bad storage.
Seizure from lack of lubrication or damaged internals (timing chain, bearings, pistons, connecting rods ) can also lock things up.
I would remove the spark plugs, look inside with a flashlight, remove the valve cover to see if the timing chain is intact. If first two items check out OK drain the oil and inspect it for metal.
Keep us posted. If it is just stuck from bad storage you may be able to get it loose. Do you have any history on what happened to it?
Joe Alexander
Blacklick, Ohio
