23rd Jan 2024, 22:09

Timing chains were (past tense) part of the engine components designed to last the life of a vehicle - I remember our old Hillman having a duplex system (double-chain). Timing belts that came after were an expensive maintenance item - during the era of much easier engine bay access, mechanics charged at least 4 hours of labour on top of the belt cost (and eventually the rollers, tensioners, and even water pumps and the thermostats behind them got replaced "while they were down there"). Cars would get traded in before the 4-year/80K km timing belt replacement was due. Then they went back to chains and people thought, hurrah!

But for some reason, suppliers didn't seem to know how to make chains that didn't stretch anymore, or chain tensioners that didn't wear out and cause the chains to skip a tooth. Engine designers, no doubt with bean counters looking over their shoulder, weren't designing duplex chain engines (which would've mitigated chains from a poor batch with some luck), and worse, in some designs, put the chains at the back end of the engine (because they're supposedly good for the life of the car), so your mechanic couldn't even check the chain tension from the oil filler cap, but also often needed the engine out (on a RWD vehicle) to change them.

Or is it that engines have become so powerful that the chain designs that served 62-105bhp Ford Cortinas are simply more likely to fail with increasing torque of modern engines?

If timing chains were meant to be a maintenance item, they would be fitted to be easier to replace, like belts with bolted covers, and not (in some vehicles) mounted at the back needing the engine to be removed to access (I'm looking at you, BMW).

23rd Jan 2024, 23:21

You mean the ones that usually last the life of the engine?

27th Jan 2024, 09:44

I would refer to the above comment to answer your question.

28th Jan 2024, 16:41

What question? All 8 vehicles that I've owned in the past 30 years had timing chains that never needed replacement, some with over 200 thousand miles. No need for me to refer to the above comment when we're both on the same page.

29th Jan 2024, 21:57

Then the answer to your question is, yes, the one that usually shouldn't need replacing. It's not universal any more though, the way it used to be when they were faultlessly durable. Them and the tensioners.