We have two 84 300d's, my wife 300td has 210k and mine has 176k. Both engines are very strong and start up in the coldest of weather(60+!!) here in San Diego. I have changed the oil every 3k and valves adj. every 15k. The previous owners took good care of these beauties but....given the milage, when should I have the timing chains replaced?? My mech said they look fine with not much stretch in them?? Can this check be done during the valve adj.? He gave me a price of close to $600.(each!!!) to have it done, which includes replacing the guides etc.. Both engines sound very tight etc... Thanks for your help