B+S 22hp very hhi crankcase pressure blowing oil out dipstick tube

started up the husquarvana 46" YTH 22V46 riding mower, BS 22hp intek 400000 series engine. 
the mower was engaged there was a noticeable noise and vibration like the blades or something was unbalanced.
disengaged the mower and the noise was still there. it subsided about in the hour cutting grass i heard it a few times.
the next time i went to start it up and the battery wouldn't/couldn't turn the engine over, there was resistance at a certain position of the crank, if i manually turned the engine over by hand i could feel it, like cylinder compression.
going past that spot the engine will turn over and start, clouds of white smoke come out the exhaust and the engine only runs 3-4secs and shuts down, taking the dip stick out and starting the engine causes a lot of oil to blow out the refill tube.
if it were a car I would say a blown head gasket...?
whatever it is sounds like major works and $$$ to fix.