Is that the metal type with the dry (green?) heat activated thread locker on it? It has no elbow (bend) to it, right? If so, try putting a bit of oil on the threads and using a deep drive socket (just bigger than the inlet size) to apply pressure to the top of the valve while you turn the valve with a wrench, be careful not to push the rubber grommet through. I ripped a grommet once taking out an old on of theses types, they are tough to install but solved all of my oil consumption issues. PS grommet from a honda passport will work.. well sort of, the honda has thinner valve covers and the grommet is sized according to that.