With the plugs out and the tranny in neutral, you outta be able to turn the engine both ways by hand just by grabbing on to the fan.
If it won't turn that way easilly, then you got somethin' stuck, bro.
Get ya a funnel and a 1 gallon can of WD40 or Kerosene and fill those cylinders up and let it soak for a few days, giving it a wiggle in the mornin' and night.
Lube the crap out of the top of the motor, too.. and do the valve spring wood & hammer smack trick to make sure all your valves are doing their thing.
As it's been said before.. the penetrating oil/WD40/Kerosene method can take time to soak thru and loosen things up.. patience is the key.
