im doin a engine for a friend and come across a few niggles , first, two off the head bolts didnt want to come all the way out without being unscrewed for the last 20 mm,?,,second, one off the bolts had a slit down the lenght of the threaded part ? .im getting new bolts ,,. it was the rocker shafts that had moved into the holes that the bolts go, is this a comman problam, and has anyone seen bolts with slots in , or has this been done by previous owners ,,

Usually when the bolts have slots in them its for woodruff timing keys

ya i know about keyways an slots ,but this is a head bolt that screws into the crankcase,, !!

Must just be from the past owner being to lazy to replace it?