When the engine is forced to turn over with the intake valve open, but the throttle body/carb closed, you produce high vacuum. I think that your right about it pulling oil past the seals/guides. I'm not familiar with those engines, but if there is a crack in the head or leaking gasket that can get oil into the cylinder under vacuum, that could be the culprit too. I'm thinking of those infamous print-o-leak symptoms in FE's where the oil is pulled into the intake tract past the intake gasket and the engine smokes from one cylinder.
http://www.supermotors.net/vehicles/registry/9026
