So you mean a link type chain and not a roller type?
I think it's worth noting...chains don't really stretch. Rather, they 'seat in'. In other words, the metal isn't stretching...it's more a case of each of the hundreds of joints finding their final resting place relative to the others.
I coulda sworn the better chains were 'pre-stretched', meaning they were run under some tension to help accelerate that seating process.
Let's suppose you could take a 'stretched' chain off an engine with 20,000 miles on it. Then, reinstall it with slightly larger OD gears that used up the added length.....you'd have a tight chain again and I don't think it would keep 'stretching'.
