"disallow" <loewen_t at yahoo.ca @> wrote in
news:7603b66467228bb297e4cee5295c6998@localhost.ta lkaboutautos.com:

> Well that sucks. Though I'm not an engineer,
> hopefully Honda had their reasons for doing
> this, and it wasn't just a cave to pressure from
> everyone who is scared of timing belts.
>


It's in response to Toyota, who made the move to chains some years ago. The
idea is to be able to claim longer service intervals.

The reason chains are getting a bad reputation is because in the old days
nobody expected their OHV engines to last much longer than 100K miles, and
most chains were good up to at least that figure.

However, engineering was paramount. A good, short, OHV chain would last a
long, long time. A long OHC chain on the other hand, might last less than
100K before eating through the chain cover or breaking. Some OHC engines
had chains that were single-row, in addition to their excessive length,
both of which were very bad for longevity (think Triumph Stag 2.5L V8).
Conversely, the 1972-82 Toyota 2T and 3T OHV engines had robustly designed
double-row chains. With regular oil changes they would eventually get very
noisy, but still easily last over 200K.

With people now getting over 200K regularly on all kinds of engines (with
decidedly variable maintenance), they're getting to the limits of chain
life, hence the problems you see. Also, some manufacturers used fiber
sprockets in an attempt to quieten chain noise. Phenolic is not the most
durable material out there.

Toyota's current designs shorten their OHC chains by running the other cam
off a gear from the chain-driven one (like their belt-driven engines).


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TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/