from what i understand the head of the bolt snaps off leaving the threaded portion in the hole. as jez said, he got lucky and was able to remove the rest with long nose pliers, but ive heard worse stories about having to get them drilled ut and re-tapped - nightmare that isnt worth it imo. to check the general health of the engine, when i do an oil change i may take the rocker cover off and just check for any wear on the cams, cruddy deposits ie slimy oily residues gunking up the crevices in the head but so far been ok. i think that changing your oil at a decent interval according to the use of the car is THE most important thing. when i had my fto i used to change the oil every 3k/6months without fail, then i did a service and tappet adjustment on a mates car with less miles on it and was shocked at the state of the valve train - covered in crap, now he is experiencing smoke which leads us to think the valve stem seals or rings are on thier way out (n/a) - all this has made me extra vigilant with my servicing on the silvia, its too good a car to neglect:nod:
15 year old fto engine 75k
10 year old sr 45k