I have seen a few of these problems on 420s and 500 engins. I have never seen a broken chain but have seen broken cams and cam towers and many bent valves on the left head. In every 6 cases I have seen, there was at least 1 broken guide. I believe when you pull the front cover you will find that one of the lower guides is broken. I personally believe that when a chain jumps timming that the front cover and oil pan need to come off and all guides replaced. I think that part of the problem is that the chain changes direction so many times, the load is constantly changing and the chain starts to vibrate and fractures an old guide which causes all the problems. I will agree that the chain is the weak link in the V8 engins but with proper maintaince, they will last forever.

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84 500 SEL (307,xxx miles)