It's odd because the dipstick just slides down into the oil pan without going through anything else. You're getting smoke from the dipstick hole though, yet, there is no combustion that occurs in the oil pan, it's all in head. So, I'm wondering what other kind of smoke could be coming from there. Are you sure it's coming out of the dipstick hole? Could you possibly have oil that's dripped onto the outside of the hole from when you pulled out the dipstick that's smoking up due to the heat?