Why the switch from timing chains to timing belts?

Dear Car Talk

Dear Car Talk | Apr 01, 1999

Dear Tom and Ray:

I'm old enough to remember when cars had steel timing chains instead of rubber timing belts. Finding a broken timing chain was as rare as finding a chicken with teeth.
My question is: Why did manufacturers switch over to timing belts instead? If they stayed with chains, at least that would be one part that would outlast the car itself.
How 'bout it? -- Charles

RAY: Well, it's true that timing chains generally do outlast timing belts. And some manufacturers still use them. Nissan, Saturn, Ford and others still use timing chains
on some of their cars. But timing chains don't always outlast cars.

TOM: You're probably thinking about the '50s and '60s. Back then, you were thrilled if you got 100,000 miles out of a car. And in those days, yes, timing chains usually
did outlast the car. But now that a lot of cars are going 150,000 miles or more, timing chains often have to be replaced, too.

RAY: As an example, I managed to get 229,000 miles out of my '67 Pontiac (which was very rare in those days), but I had to put three timing chains in it.

TOM: Belts do have their advantages. They're cheaper, quieter, lighter and easier to replace. They're also better able to handle the longer run necessary for overhead-
cam engines. In the old days, a timing chain only had to be a foot long. Now, with overhead-cam engines, it has to be 3 or 4 feet long, and for that kind of length, a belt
is not only a lot quieter, but more reliable, too. When you use a chain for that kind of length, it's more likely to loosen up, slap around and eventually break.

RAY: So it's a trade-off, Charles. Timing chains do last longer, but not necessarily the life of the car. And when they do break, it's a big job and a lot of money to
replace them. So I'd call it a tossup, and I wouldn't base a decision to buy or not buy a car on whether it uses a timing belt or timing chain.

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?(C) 1999 by Tom and Ray Magliozzi and Doug Berman
Distributed by King Features Syndicate, Inc.

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