Timing

If the timing swings are not as severe when the engine is cold but gets worse as it warms up, your chain is shot. That is the Achilles heel of small blocks. The timing chain will stretch so much that the engine will quit running somewhere around 50-60K miles. At least that's been my experience and I've owned a bunch of them over the years. A new chain (preferably a double roller) and a Mopar tensioner will last much longer. Hope this helps.