New bearings, difficult to rotate the crankshaft.

I have changed</SPAN> bearings and pistons in my 273. The problem is that it is difficult to obtain the crankshaft to move. Could it be enough to prime the oil system, or do I need to open the engine again? The latter option I'd prefer to avoid. All the bolts has been tightened to proper torque, so that is not the fault.</SPAN>