Well we will find out when I take it apart I guess. It could have been done years before I bought it (the previous owner didn't) at 165k miles.
Garak on this site has experience with a fleet of cabs, lot of them with this engine and he doesn't recall having any timing chain issues.
Lots of them went over 200k. Most that did fail wore through the timing cover before jumping.
One of my previous Caprices was an 87 with the Olds 307. I replaced it's timing chain at 160k miles and it had some stretch but the original nylon gears were still intact with some minor stress cracking starting. I hear lots of people say they only went 80k but in my experience that hasn't been the case. My friend who was a ford mechanic back in the 80s said a lot of Ford's were wear out by that mileage but it doesn't seem to be the case for the Chevy or Olds engines.
Quite an interesting subject, And I would like to apologize to KGMtech for derailing his thread!
Oldsmobile engines are a totally different design, While I never worked at a Olds dealer.....I spent years at a Cadillac dealer. Cadillac used the 307 & 350 Olds in a few models during my tenure & did customer-pay service work on 368, 425, & 500 Cadillac's quite a bit.
ALL these engine used nylon clad aluminum cam gears & didn't have near the failure rate as the small block Chevrolet! I don't know exactly why that was? Harmonics, Different oiling, Different materials etc? People like to lump all GM engineering into one, That is more true now but wasn't years ago.