Then they started reducing the amount of material they could minimally require in order to still produce something resembling a chain. Newer chains are narrower, made of thinner steel, lighter in all aspects, you name it -- all in the name of reducing drag and friction, and thus the relative load on the chain increases and the strength of the links and pins decrease. Add in chain tensioners adhering to the same philosophy. Bang! We have timing chain failures.
If you want ultimate resilience, get a car with non-interference valvetrain. Doesn't matter if the timing breaks up, you'll just install a new chain/belt and continue.
I've owned several high mileage vehicles (over 300k) including Toyota 22RE, 3RZ, and Chevy LS with their original timing chain. Now that I think about it, does the LS even have a tensioner or chain guide?
From an enthusiast's perspective, a chain is probably preferable, because it tends to give you some warning before it fails - you might hear a rattle at idle, you might have problems with starting or misfires, you might get a check engine light and an EBD-II code from the timing sensors. That's a much less scary prospect than the potential for a sudden and catastrophic failure of a timing belt.
From a manufacturer or dealership's perspective, belts have some clear advantages. Unless there was a manufacturing defect in the belt, they'll almost never cause trouble if replaced according to schedule. That has obvious liability implications - it's not their fault if the customer ignores the specified replacement interval, but it potentially is their fault if a chain wears faster than expected. BMW, VAG and Jaguar Land Rover have all recently settled class action lawsuits related to the premature failure of timing chains.
Previous gen GTI was a belt. Garage told me they preferred belts because people know they need to replace those. People aren't expecting to be told your chain needs to be replaced plus it's much more expensive and labour intensive.
Never heard of Honda having problems with chains, though. Some of their motorbikes even had gear driven cams! (VFR I think).
They are by no means immortal, but, by design, should have a much longer lifespan than belts.
> Virtually every engine I know with a chain ends up either regularly failing early [..]
But I have no idea which early-failing models OP is referring to, as the engines I know about where quite reliable. (As in 1e6+ km reliable, with chain maintenance per manufacturer guidelines.)
For example, on BMW Minis, which all have timing chains:
- 1st gens Minis (2002 -> 2006 roughly), with Chrysler engines, have a bulletproof engine, and replacing the timing chain is a rare occurrence
- 2nd gens Mini (2007 -> 2013 roughly) with PSA engines modified by BMW have a suicidal engines, especially the pre-LCI (2007 -> 2009) engines, that are known to often break timing chain guides. The symptom for that is named "death rattle", which is chain slap.
- 3nd gens Mini (2014 -> 2022 roughly) with BMW engines are so far known to be pretty bulletproof. Note that some of them now have high mileage with no large-scale issues.
So a well-designed engine with a timing chain is preferable to a timing belt. But a timing belt is preferable to a problematic engine with a timing chain, which will break at the most inconvenient time and leave you with an unexpected large bill.
Buuuuut, there's also modern Opel engines where timing chain is guaranteed to kill the engine if not replaced every 100k km.
So it really depends on the engine rather being simple chain vs belt.
As with all things, the build quality and overall design will overrule single atomized design decisions. GM iron dukes have geared cams, which should be frickin' bulletproof, but they use a nylon spindle that tends to blow apart under variable load or just using weird fluids.