Timing belt vs timing chain

Why do car manufacturers stick to timing belts? Timing chains seem to be so much better, they last longer and dont snap! Why has no one made a conversion kit to put a chain into a alfa engine?

I have timing chains in my Spider's, you'd think the newer Alfa's could be converted back or the belts redesigned.
I just had a new timing belt/ water pump put in my Acura today, it's done 90K kilometers since the last one.
We don't every hear of belts breaking here.

thats what i was thinking, if someone could produce a timing chain kit that cost roughly the same a timing belt kit, they'd make a FORTUNE

The thing with chains is that they need to be lubricated, where as belts don't I reckon that would be the most difficult/expensive part of any conversion.

Those with 2.2 JTS engines should be slightly wary of the camchains, I read on Honest John that 2.2 litre Vauxhalls with the similar engine are suffering cam-chain failures due to lubrication issues. I hope the Alfa Unit is immune to this.

I've also heard of chains stretching with time. I don't think they're the panacea everyone thinks they are, but are still probably a better bet than a belt on a high-revving engine.

Originally Posted by phylet

Why do car manufacturers stick to timing belts?

Well, they don't. Manufacturers like Alfa and BMW are back to chains on the new (petrol) engines.

Originally Posted by selespeed

Well, they don't. Manufacturers like Alfa and BMW are back to chains on the new (petrol) engines.

does this mean we can get chains put on the old engines too now if Alfa r making them for the newer petrol engines?? these cam belts r a pain as they need replacing before u even get to 50k!!

BMW state that chains should last the life of the engine. 20 Years ago chains were known for stretching and being noisy but I believe all those issues are now resolved.
IMHO chains are much more reliable than belts.
As for the Vauxhall problem of snapping chains, according to Honest John that was resolved in 2002, 4 years before Alfa launched the 2.2.

Belts are cheaper, quieter & don't need lubrication. Chain wear (seen as 'stretch') also affects timing, but probably not to the extent that it would be noticeable on a road car.

Chains do break, but chain breakage is nothing like as common as belt breakage.

Chains tend to be a lot harder to change than belts.. At least they tend to give some warning before snapping though unlike a belt.

Originally Posted by Romeo Red

does this mean we can get chains put on the old engines too now if Alfa r making them for the newer petrol engines?? these cam belts r a pain as they need replacing before u even get to 50k!!

No, chains are inside the engine, the chain is drawn through engine oil as it revolves, this constant lurication makes them really durable. Conversely, belts are an external component. There is no simple way to convert from belt to chain.

BTW my BMW diesel has no chain replacement built into the service schedule at all. Then again, my JTD was only £197 to get a new belt and pulleys - there's no excuse for neglecting a belt change!

The old Saab engines (up to a couple of years ago) all had timing chains. I had a poverty spec 9000 which did over 200k miles on it's original chain and ran very strongly into the scrap yard... Turbos tended to need a chain somewhere around 100K miles but they were hauling around 2 tonnes of singleminded Swedish engineering with a 230hp 2.3 litre engine....

From memory a new chain was upto £700...

Cheers
John

My 164 is still driving around like new on its chain with 160k miles on it.

Can't recall a properly maintained 164 TS requiring a chain before the engine wore out some way beyond 200,000 miles.

A few cars have badly designed chains. They are the exceptions. Nissan Micra mk1 broke chains, Ladas had chains made from linked spaghetti hoops, Stags had single row chains that stretched.

The big advantage of a chain is that in most situations, if it is starting to go wrong you get plenty of warning before it gets critical. Not so with a belt. Also I can't think of a worse enviroment for a belt to operate. Heat, grime, oil, spray. All of which knacker the roller bearings and degrade the belt itself, which also suffers fatigue. Chains by comparison bath themselves constantly in freshly filtered hot oil (This is not any oil, its M&S Oil )

You get my drift

AlfaLincs

have a look on Saabscene (9000) and there is no end of issues with timing chains, replacement is more than the chain itself, its the sprockets as well as they also wear along with the guides. Bills for £1500 are not uncommon, and that is before they snap, which they do or jump a tooth. Typically chain work is needed at 100k miles, some earlier.

Besides I can to a belt, but I would find doing a chain a bit more challenging.

I had the chain replaced on a Mercedes 190e Cosworth .......... about 6 years ago.......... The sprockets were wrecked as well (If your chain is shot, the chances are the sprockets will be as wel. just like on a motorcyclel).......... cost me over £1900 to get it sorted.

Peter

Not often a chain actually snaps, the Saabs engine was the same engine block as the Dolomite Sprint & they had a problem with the chain guides wearing out quickly & the chain would then jump a tooth or 2 & bugger the valves . I would have thought most engines were redesigned by now ??
Nissan went to chains about 4 years back.

Bobster is right of course. Saabs have had an inherent problem with chains going right back to when the first 99 used the Triumph Dolomite engine. My dads 99 was alright, but his 900 needed a new chain well out of warranty and Saab paid for the lot.

I don't think that any of this changes the simple fact that in the wider scheme of things chains cause far fewer engines to destruct, and generally last an awful lot longer than belts. Changing a chain is not common, its an exception we all note. How many motorbikes use belts for the transmission. Some tried it, but not for long. They can't afford to have such a vital component fail. For reliability and longevity the timing chain wins 99 times out of 100.

You don't tend to see ads on ebay saying 'cam chain gone' do you. You see lots saying 'cam belt gone'.

AlfaLincs

My mates Mondeo ST200 V6 has a chain and he says he will never have to replace it for as long as he has the car. Apparently there is no stretch or wear on those and its guarranteed for the life of the engine. Lucky get.

It's power vs reliability, with the chain the enigine wieghs more and so pound for pound in general a belted engine produces more power, also this is down to all the extra moving parts that are required, pushrods and such, if you wanted a 16 valver without with a chain just imagine how long the chain would be and how much backlash there would be....if there wasn't pushrods in it.

If anyone finds a conversion kit for a GTV let me know...

Originally Posted by AlfaLincs

Ladas had chains made from linked spaghetti hoops,

Lada's didn't have any of that chains or belts nonsense at all.. they had push-rods!


Chains will always stretch, as the pins will wear, even if the chain is permanently immersed in clean oil.. (albeit then very slowly). Stretch can be compensated for by a relatively simple sprung sprocket tensioner though.. so it's hardly a big deal.

If the chain wears or the tensioner stops doing it's thing, you risk the chain lifting off the sprocket (camshaft end being the most vulnerable) and when it does that, it will either leap off the sprocket and jam the whole cam drive (even Twin Spark owners can only imagine what that will look like! ) or it will rub against the inside of its cover.. making a rattle. If it's internal to the engine (to immerse it and the tensioner in oil) then it will dump that metal swarf into your oil... So, chain lubrication and tensioning is rather crucial.

I can only imagine that a cam-chain is more expensive to make and more expensive to assemble than a belt, to explain the rise of the belt.

The best solution (apart from push-rods! ) has to be gear driven cams.. no maintenance, no adjustment, no tensioner. Dunno what's wrong with them, that nobody is using them..

Ralf S.

my old merc 240d had 2 chains, and over 250,000 miles when I sold it