Benedict, after thinking about it some more I retract my recommendation to immediately replace the timing chain. After reassembling the engine with new timing chain guide rails, tensioner and reconditioned head(s) measure the timing chain stretch. If acceptable, don't bother replacing the timing chain. Of course, that presumes the labor to check the timing chain stretch is less than the cost to purchase/install a new timing chain. It's likely one of the old timing chain guides failed and caused the timing chain to jump.

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Fred Hoelzle