I'm rebuilding a 159 inch Case gas engine and when I was putting together the head one of the exhaust valve retainers had the springs and ball bearings fall out. Before starting the rebuild process I looked at parts on lots of internet sites and remember seeing them once but now I can't seem to find any. The guy at the machine shop is looking but did comment that the last time he did have a hard time locating some. The valves, guides and seats are all new. Are these rotators really required or are they just another gizmo that can cause more trouble than they help? Can they be gutted and used plain or replaced with the plain style like the intakes use?