Engine oil is getting into the inlet manifold and causing blue smoke in my rebuilt engine could it be a blocked breather?

it could b valve seals, head gasket, blocked oil galleries, piston rings, cylinder bore. oil drain holes from the cylinder heads to the oil pan get clogged and oil puddles and gets pulled down the shaft of the intake valve and burnt with the air/fuel charge causing blue smoke. pcv valve(positive crankcase ventalation), if clogged causes a vaccuum during intake stroke . damaginging seals and gaskets and a rebuilt engine probably has a few of these. does it smoke real bad after being run and then sitting 4 a short time?