Could be a bad chain guide or tensioner.I've got a 85 Nissan 720 4x4 2.4 with a Weber carb.Had her since 1993.It had 108,000 miles on it when I got it.Not long afterwards,Carb went bad,no one could rebuild it,tried 3 places.Finally took to Nissan Dealer,they told me that the carb was a bad design and they could not rebuild,they told me it was junk,they were right,not long afterwards motor went bad,so I got a remanufactured Jasper motor,with 3 year-or 100,000 mile warranty,got it in 2009,I now have 61,000 miles on it with a new Weber carb and it runs awesome,never ever had a timing chain issue,speedo now has 344,000 miles on it.Had the engine installed by a Jasper engine installer,a pro,seems like whoever has been putting timing chains in your engine is clueless on these 2.4 engines,our Nissan's have a history of head gaskets blowing,never timing chain issues.Here is a link on how to replace your Timing chain.
Repair Guides Engine Mechanical Timing Chain And Tensioner AutoZone com Here is a photo of mine,need more help,let me know.