Blow-by usually comes out of the draft tube,if lower piston rings are affected. It will smoke out of the exhaust,if the upper rings are not seating,or cylinders are worn beyond the ring tolerance. I hope a water jacket in the head isn't cracked. Coolant may seep into a nearby cylinder,and it will smoke until the head expands enough to seal the leak,and evaporate the coolant. A bad head gasket may produce the same effect.
