Belt vs. chain for cam drive

[David Head]

Don't talk to older Mercedes owners about timing chains. Late 60's Pontiac owners either. Until the advent of double row chains and better build quality in the late 70s/early 80s timing chain life was under 125,000 miles. Pontiac tried to go to a plastic cam gear to run quieter with disasterous results. Double row chains were the first priority for your soon to be hot rod in the 60s and 70s.
I've changed plenty of good old Chevy timing chains - its one of the first things to check on a high mileage engine that seems to have lost its oomph. Turn the crank backwards and see how far you have to go before the distrubutor turns. I've seen them jump time, and seen chains break and gears break.

David.Ullrich at ferguson.com wrote:

> You have a point, but have forgotten just how long timing chains last. If engineered properly they will last as long as the engine. Lets take for example the good old Chevy V8 in either 305 or 350 CI displacement. That engine has a timing chain and nobody EVER changes them. I'm also into Impalas (I have an 85 SS and previously had a 78). I've never heard of the timing chain ever breaking or skipping a tooth, ever. On my previous 87 Impala with a 305, it had over 425,000 miles on it when I finally replaced the engine. The timing chain had NEVER been touched. Sure, it had stretched a tad and there was a bit more play in the timing, but I could still tune it to within 1/2 degree. The 85 SS has a HO 255 HP 350 has almost 150,000 on it and the timing chain hasn't been touched and hasn't even stretched yet. So, if Audi did their homework, the timing chain shouldn't ever have to be touched, at least until the engine has to be pulled for a rebuild...
>
> Dave
>
> 1987.5 Audi Coupe GT "Special Build" 2.3 - Anthracite Black
> 1998 VW Passat GLS 1.8T - For Sale CHEAP
>
> -----Original Message-----
> From: Mike Arman [mailto:armanmik at n-jcenter.com]
> Sent: Wednesday, May 08, 2002 4:17 AM
> To: quattro at audifans.com
> Subject: Belt vs. chain for cam drive
>
> >From those pages:  "The toothed belt previously to be found on the
> >engine's front end has been replaced by a chain drive to its rear."
> >About  Time, hoping they do this to ALL their engines.  No ultra pressure
> >hydraulics, no timing belts, etc.  Yeah.
> >
>
> I'm not entirely convinced that the chain drive is an improvement,
> especially as it is located on the rear of the engine, where there is NO
> access to it unless you pull the engine (and tranny).
>
> My perception of the problem is this - since the chain is out of sight, out
> of mind, the only time any attention will be paid to it is when it breaks
> or skips some teeth, and then the damage to the rest of the engine will be
> horrendous. Take a look at the W-12 picture, and you can just see the chain
> at the rear of the engine . . . and notice how complex that engine is.
>
> At least the rubber belt is fairly easy to change, and (at least on the I-5
> engines) not expensive. Heck, we change oil, don't we? Changing the belt
> every 60,000 miles is just good preventive maintenance. Changing the chain
> is going to be a HUGE job, and like as not, won't get done until it breaks,
> and then the entire engine will be scrap metal.
>
> Result - Audis will go down in value, quickly. Why? The "older" ones will
> be in the junkyards because no one will pay the huge amount needed to fix
> the engines - and by "older", I'm talking about cars that may be only five
> years old! 100,000 miles in five years is no big deal any more - and here's
> a car which is five years old, and needs $15,000 worth of engine work to be
> a $20,000 car. Ouch.
>
> As the word gets out that there are LOTS of late model Audis in junkyards
> because once out of warranty, no one can afford to fix them, the resale
> values of the ones that still do run will plummet, and the depreciation
> will increase drastically.
>
> Don't get all excited if this scenario sounds familiar - the last time it
> happened, there was NOTHING wrong with the cars, and it almost killed Audi
> in the US market. This time, there will be a great deal wrong with the
> cars, and the non-existent resale values will be based in hard financial
> fact, not television fiction.
>
> I think Audi is making a mistake by not considering the entire life cycle
> of their product. Once the warranty is expired (and sometimes even while it
> is still in "effect"), they want the cars to simply evaporate off the face
> of the earth, thank you. As a result, older Audi's are tough to sell and
> don't bring much money, and this hurts the sales of new ones because people
> KNOW they are going to get hosed at trade-in time.
>
> Mercedes has a slightly smarter approach. They seem to be interested in
> making parts and service available for anything they have ever built, and
> as a result, there are more "classic" Benzes running around. People then
> say "Hey, those cars run forever and hold their value, too - I want one!",
> and a 90s vintage MB which cost just a little more than a 90s vintage Audi
> when new sells for a LOT more now, and it isn't really a better car.
> Example: compare the current selling prices of a 1991 190E and a 1991 90.
> Mercedes is thus perceived to have value, and they get ferocious top dollar
> for their cars, wheras Audi, whose flagship cars are similarly priced, has
> a tough time.
>
> Solutions - 1) design for durability beyond the day the warranty expires -
> this supports the market and price point for the cars still IN warranty. 2)
> Support the out of warranty vehicles. A pristine twenty-year-old example of
> your marque is a darn good advertisement, and you can make money selling
> all those parts, too!
>
> And I'm SURE Audi isn't listening, but I feel better now . . .
>
> Best Regards,
>
> Mike Arman