Can anyone tell me other than the potential for the pistons hitting the valves at extreme stretch are some other indicators of chain stretch. I notice punch marks on my cam other than the factory mark. Is this a indicator that there has been work done on this auto before? My auto is a 1990 350 SDL with a 603 motor. I have searched and found how to check for stretch but no real info on symptons. Thanks

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Who needs spark plugs.