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do timing chains actually stretch? some old duffer in the pub reckons the pins in the links wear out but the actual links dont stretch, so he says the timing chain shouldnt jump off the sprockets, unless they are worn to near enough smooth, what makes me ask is my t/chain rattles like a gooden but ticks over like a dream , and never misses a beat , im trying to put off changing mine cause it looks like a shed load of hassle.. opinions please!!
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In a word, a chain does stretch as the pins wear, and with a long chain the difference can be considerable. Even with a very short chain as in a real (i.e. non-VW) Skoda 1300 engine, the chain starts to chatter audibly after about 15,000 miles, and the ignition timing (distributor driven off camshaft) begins to scatter a bit, without much affecting performance.
It shouldn't jump a tooth on the sprockets though, unless there's a tensioner problem. But of course it will eventually break when the pins get worn enough.
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Yes, chains wear, but the link side plates don't stretch. The stretch in the chain appears as the extra play in the pivots is taken up. Typical test for wear on, say, a motorcycle chain is to hang the chain up and check the length of a specific number of links, discarding the chain when this exceeds a specified value. Worn chains will increase sprocket wear as the wear in the links prevents the load being taken on a reasonable number of teeth on the sprockets - all the load ends up being taken on the first tooth of the sprockets. So always best to replace both chain and sprockets.
The overall 'stretch' does slightly retard the valve timing too, of course.
JS
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>>The overall 'stretch' does slightly retard the valve timing too, of course.
Yes, one way to keep an eye on this is to read the cranshaft angle from the pulley when the cam is in a perticular repeatable position (ideally when you can insert a timing pin in the cam sprocket if the engine is so equipped).
By comparing the reading when new and when worn, chain stretch can be evaluated without any dismantling. Once you have more than a few crankshaft degrees stretch, it's a good time to change the chain.
Number_Cruncher
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My Skoda Felicia (1.3) is as quiet as a mouse at 35K miles, well , apart from normal engine noise.
Is this an urban myth?- Now Morris Minors did rattle, and A35s , as I had them
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"Is this an urban myth?"
I know a neighbour's family friend who have a 2.0i D.O.H.C. (Chains Driven) Ford Sierra with 200,000+ miles on the clock and never had any chain noise or any other known problems, because he changed the engine oils twice a year using Full Synthetic.
I recall that he was telling me with using Mineral Engine Oils is a quick way of destory the engine parts as it doesn't lubricate corretly when starting from cold or running on hot during high speed and also when the sludges are formed that is where the engine parts are get worn so quickly.
He did make me to think twice about pouring cheap or using Mineral Engine Oils in Engine, A.T.F. - Automatic/Power Steering and Axle Oil, it's the same that you eat healthy foods to be healthy, that is the same way for your motor vehicles!
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if you can live with the noise milkyjoe then leave it alone as you will put a new chain and tensioner on and it will be noisy again in a 1000 miles,as said you would need to change the sprockets as well to get long term quietness
you really only want to be changing chains on these engines if you are wanting to achieve a sale and some customers have already walked away because of the clatter
motorbike chains are obviously a different kettle of fish
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The laws of physics say it must wear or you would have eliminated all friction; something not possible on earth.
To reduce wear, reduce friction. To reduce friction change the oil more often, and use a good quality oil, preferably synthetic, which is very good at reducing friction during the very critical first 20 seconds of start up.
Simple really.
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Telling us what type of car you have might help us diagnose if you actually have a chain problem or you need to adjust the tensioner. For example, old Austin Maxi's (ah, those were the days..) had an automatic tensioner that you could adjust (even though it was automatic) using an allen key. Maxi's were renown for tickover chain rattle (there was nothing wrong with the chain) but was easily remedied as described above.
And your car is......????
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These are the views of Robin the Technician with 35 years in the trade. I fix, therefore I am...
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Telling us what type of car you have
Chances are it's his Fiesta. ( www.honestjohn.co.uk/forum/post/index.htm?t=51676 )
Lost count the amount of times I've had to edit it into the subject header later, despite the sticky notices at the top of the page asking people to do so when they compose their question! DD.
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ps, the question did however start off as a general one about timing chains, and it wasn't until later in the question that the reason for asking was mentioned. DD.
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SNIP, it was a general question!!!
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