1989 4runner son said it made a bad noise and was low on power, he limped it home. removed plugs 1-3 look perfect, plug #4 is sooty compression test 155 in all 4 holes. remove valve cover, see Ex valve rocker arm for cyl #4 is broken, cam looks fine. in an attempt to remove the Rocker arm assembly one of the head bolts snapped just below the surface of the rocker arm support tower. now I cant remove the rocker, cant remove the cylinder head.. wtf? any ideas? the rusty hole is the broken head bolt, its soaking in PB blaster although I think that to be a futile attempt. and yes I know its sludged up, I will put it back together with a much hotter thermostat.