I am in the process of a teardown of a junkyard motor to start my build. But I have encountered an interesting problem. The crankshaft rotates smoothly, (plugs out) but stops after its been rotated about 180* in either direction. I was using a breaker bar on the crank pulley bolt, but that came out. Any thoughts on what the issue might be here? Possibly a rust ring in the cylinders from sitting? If that is the case it doesn't matter as I'm overboring anyways. Anybody encountered this before? I'm new to major engine work, understand the principles but haven't had much wrench time.

 

Remove the head and oil pan, you should be able to see what is preventing the crank from making a full rotation.