Right to start with a roller chain isn't nearly as strong. They are not "constant tooth contact" so you get more spark scatter from the distributor. There is also no tensioner to keep them from flopping around when they get loose, and they do get loose in a hurry. It's my opinion that lacking a tensioning system allows them to really start flopping around when they get loose and accellerates the wear.
If you've ever peaked into a chain driven 4 X 4 transfer case you will NEVER see a roller chain there. It wouldn't last to the bottom of my driveway in a 6000 lb truck on hard pavement in four wheel drive mode.
The roller chains also have multiple wear points, and many are low quality. The only one I'd even look at for any of these engines would be the high end Cloye's or Rollmaster with the IWIS chain on it.
I've pulled down a good many engines several years after full rebuilds and you'd be surprised at how loose the roller timing sets are. We don't get accurate feedback with this sort of thing simply due to the way these vehicle are used. Most don't see much more than a couple of car shows every summer, couple of trips to Dairy Queen for ice cream, and maybe one or two trips to the local track to make a few passes on a Friday nigh test & tune session.
I actually tried one of the "high end" Rollmaster 9 keyway double roller sets back in 1999. It was highly recommended to me and came with an engine "package" I bought when building the first 455 that went into my Ventura. I was racing the car a lot back then, and lots of street driving. Four year later it had to be replaced. Got so loose you could just about walk it right off the gears!
I used a 3/4" wide Cloyes in the next 455 build in 2008. In 2022 the timing cover developed a coolant leak and had to be removed. I bought another Cloyes Morse type timing set to replace it. When I got the timing cover off the chain was still pretty right, with only witness marks on the gears. Put on new gaskets and buttoned it back up and good to go for another 15 years or so......
Pictured below is one I bought off Ebay recently and the type I prefer to use. Steel sprockets and 3/4" wide chain. One of these will easily last the life of the engine......
