does the engine or trans. have any leaks? another sign of wear. if not, as previous posters mentioned, i'd leave alone. good call on injector rebuild/replace. does it have glow plugs? if so, might be worth a check. as far as valve adj, good advice to adjust. if you've never done it on gas/diesel engines, i'd recommend getting someone over on site who knows how. & call the dealer on the intake/exhaust clearances, & whether done cold, warm, or hot. & of course replace valve cover gasket when completed. great project! like those old school machines. also great advice by jenkinsph