jim beam wrote:

> y_p_w wrote:
>
>>
>>
>> jim beam wrote:
>>
>>> FanJet wrote:
>>>
>>>> "jim beam" > wrote in message
>>>> ...
>>>> Belts are certainly good for $dealerships$. Their replacement isn't
>>>> preventive maintenance, it's scheduled maintenance - big difference.
>>>> If Honda used a decent chain, the customer wouldn't need to deal
>>>> with it. The Q45 issue was an anomaly. I'm sure there's the
>>>> occasional Honda spun bearing or some other oddity. Maybe the
>>>> customer ought to replace them every 80K.
>>>
>>>
>>>
>>>
>>> if you drive some piece of v8 detroit iron with less than 40 bhp per
>>> liter, you're not going to notice much difference with a bit of chain
>>> stretch. and cam timing errors in excess of 10 degrees of crankshaft
>>> are not unknown. belts don't stretch so they remain dead-on with
>>> timing right up to replacement day. you want a high performance engine?
>>
>>
>>
>> One forgets that chains put a certain amount of stress on motor oil.
>> If people are lax about their oil change intervals and/or use poor
>> quality oils, chains have been known to crap out. Chains create
>> their own difficulties with OHV engines. Belts don't need any
>> lubrication.
>>
> that's right - the longer travel for overhead cams is a much bigger deal
> for a chain at high revs than for a belt. belts have much less mass.
> chains for block mounted cams where the runs are short are just fine.

A chain driving pushrods is fairly short.

If well maintained, most will probably last the life of a car. If
poorly maintained, chains can stretch, jump, or otherwise crap out.
Some of the early Saturns had problems with the oiling pump cover
and how it distributed oil to their timing chains (TSB 97-T-15A).

<http://autorepair.about.com/library/faqs/bl811h.htm>

Chains are often noisier, and GM tried making them less so by using
nylon coated gear teeth. Eventually the nylon would "shed" and plug
up oil filters.