Cylinders,Replaced a ruined cylinder head with a used cylinder head

I had a spark plug blow out. The previous owner had already heli coiled the head, and that blew out, I replaced the passenger side head with a used one. With the timing chains,guides,and tensioners in place and the key way (on the crankshaft)in the 12:00 o'clock position I manually rotate the engine clockwise until it reaches the 10 o'clock then it stops. From there I rotate counter clockwise until it gets to the 10 o'clock then stops. What would cause this?

My car has 160000 miles.
My car has an automatic transmission.