I don't know what year they started using the nylon timing gears, but I know of a 1970 318 that had one that was bad enough to allow the timing chain to skip a few teeth and bend valves and pushrods.
It happens. I think the nylon coated gears were one of the stupidest things ever. It was all a quest to make the engine more quiet, but I've never in my life heard steel chain and sprockets make noise........unless they were so worn the chain slapped the timing cover.......I have seen that more than once. One on my own 3.8 Buick V6 I had in a 76 Olds Starfire. It hit the cover for so long and so bad that it wore a hole in it. I was waiting for it to wear out, because I slammed a Chevy 400 in it after that. lol
