Rebuilt engine and engine turned over fine with socket.  Replaced cam with Isky 30144 and all went well.  Now the engine will not turn over by hand.  Took off tranny, clutch, flywheel, plugs and clothes pinned each valve push rod up with clothes pin.  Still not turn. Could it be something to do with the tappets & cam - as everything went in fine when installing.  Don't want to take engine our and tear it down, hopefully something simple I'm missing