Something is overpressurizing the block and pushing the oil out the valvecovers. Unfortunately, my money is on the ringlands. They will let the chambers get oiled up and cause a smoky startup....but the plugs will also show signs of it when pulled. When you go to do your compression/leakdown test, see if your plugs still look as clean as the other set you pulled out.
Good luck with it anyway.....hope it's something minimal.