Personaly, I would avoid using petrol as an engine cleaner.
It poses a significant health & safety risk, Exposive, toxic & harmfull to the skin to name a few.
I have used Jizer as a cleaner for many years, water soluable & will air dry with the use of a blow gun.
There are engine assembly oils out there, I tend to use plain ole Magnatex, does what it says on the tin.
Looking at that cylinder head of yours & at a quick glance it would certainly look as if it has blown the head gasket.
I would investigate if this is the case & then investigate why !!??