It is possible it was something else but since I've heard what the chain sounds like before (just before it broke a few years ago and before that, though I obviously didn't understand the dangers and misdiagnosed back then) I know what it sounds like, and it really sounded like chain slap. I can't be sure, but I'm really pretty sure.

Steve the moderator had indicated in some other posts in the archives that sometimes it's difficult to get rid of all slap because of the way the tensioner works. I studied that, actually bought a tensioner to look at, etc, and I think I agree but I'm really still guessing. What I definitely can say is that, after changing that oil, the sound went away. Cold starts, whenever starts, I stopped hearing that noise. I'm posting the info here because, if someone has a car that really shouldn't slap because all of the proper things have been done (new rails, new tensioners, etc) then you might consider a lighter weight synthetic oil that works for the weather/season in your area. Also, it seems to me that if I had a car that was say around 80,000 miles or so and coming up on a timing chain change, I might give real thought, based on what I know now, to the visosity of the oil/etc and how that might affect the engine's operation at startup. As I understand it, most of the damage to an engine occurs at cold start and that is certainly the case for a timing chain. And at cold start, that's exactly when a lighter weight oil, and also a synthetic for that matter, provides less friction I think.