Ray J has re-entered the world of porn … and he’s gone from  blow jobs to nose jobs.

The man famous for making Kim  Kardashian a star hit the sheets with Joan  Rivers for a very dirty session.  Ok … nowhere near as dirty as  he got with Kim, but in old lady terms, it’s raunchy.

As Joan does so  well … they faked sex for her WE tv show, “Joan & Melissa: Joan Knows  Best?” (which premieres March 29).  You gotta watch … it’s pretty  funny.

Even though it’s all for gags … Vivid Entertainment honcho Steven Hirsch tells TMZ he did meet with Joan to discuss the  possibility of making her his first GILF star. He tells us, “I’d pay her  $100,000 right now!”