depends on the mileage on the engine and whether the odometer REALLY is right. the chain does stretch and will break. if you replace the guides about every 70k or so, you can get by on the oe chain 'till about 150k. if the guides are let go for a while after 70k, then the chain gets REALLY loose and will need replacing about 100-120k miles. if all is unknown then i would replace the chain, tensioner and guides and not worry about it. better safe than sorry. the chain breaks, then the heads come off to replace the bent valves on the left side, the right side to make sure compression is the same as the fresh left 1. good luck, chuck.