Further to burning oil issue --- heads/valves now need cleaning of carbon debris. Does the group think it's OK to turn the heads upside down on a bench to work on them? The cams, etc are still in place and I know you are not supposed to turn the hydraulic lifters upside down when they are OUT of the heads but I'm wondering if it's OK for them to be upside down while they are still IN the heads. Any thoughts on this and advice on cleaning?