I would do a compression test to see if the head gasket is gone between 5/6. I have not seen a cam go on these engines yet. Does not mean it can. I am currently in Vermont and not able to look at anything until next week.
When doing a compression test with all the spark plugs out, if you hear a slight compression squeek when you get compression on the guage and the guage reads lower then the rest of the cylinders(1-4) then you may have the gasket gone between the two cylinder. Any how good luck and I will check in when I can