Lucky escape today, was heading out to fill it up with super unleaded as could only get premium crap when I picked it up

Got to top of my drive and it starting missing and I could hear a tapping, so got it straight in garage and pulled rocker cover off, no 1 exhaust valve rocker nut had backed of and was flush with top of stud totally if the locker !





I didn't notice it when I did valve clearances, so I took a 11/16 socket and extension in my hand and could also easily turn no 4 rocker aswell ! Could of been nasty, I've ordered crane locking nuts I will change them all before I run it again