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715 posts

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  # 1780523 13-May-2017 10:11
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networkn:

 

 

 

The whole reason chains were invented, was to lessen the problems from a belt. It's the reason for it's existence. 

 

 

 

Cambelts are a relative latecomer. They weren't common at all until advances in belt technology and the move to overhead cam engines made them viable.
But gears, chains, belts.. all are equally good engineering solutions for specific applications.

 

A lightweight OHC boxer engine with the cams far away from the crank lends itself to a light, quiet belt drive. They're mechanically leveraged (small drive pulley and large cam pulleys) to put less strain on the belt, and it's relatively easily replaced.

 

Heavier OHC V8's with cams also far from the crank often use long chains - stronger, but not always quiet, cheap or reliable.

If you need something that'll last forever in extreme use – you get a heavy, noisy gear drive as used on most industrial engines.
We used to build (pushrod) V8 engines, usually chucking the factory timing chain, and replacing it with a gear drive that would last with high revs, high lift cams, and high pressure valve springs.

There's going to be a tradeoff between longevity, noise, weight, and servicability - in climatic extremes, or at the outer limits of the engine's design envelope - balanced against customer expectations. The 'best' engineering solution is often not the one used. Cost looms large in manufacturer's choice of cam drive system. Ease of replacement is somewhere down the list – as that often falls to a 2nd or maybe 3rd owner.

 

I've just reinstalled the timing chains on my 2013 SOHC 6.2 Ford – at 80K! – after the oil pressure activated tensioning system gave up. And recently replaced my wife's Subie belt at 140K which (with obligatory tensioners waterpump, oil & cam seals) cost about the same.

I have a theory those manufacturer recommended replacement intervals are very conservative. But my wife disagreed and wouldn't let it go any longer.

 

A friend and I've bought Subies for years as fix-up projects. Many have clearly NEVER had the original cambelt replaced. One barely running car we got recently with 190,000km turned out to have the original factory plugs in it – the electrodes had completely eroded away - incredibly it still ran. The factory belt still looked OK -with a little crazing. The few with belt failures we've bought all had K's in the mid or high 200's (they'd failed by stripping a tooth or idler failure rather than a snapped belt) and those were likely their original belts.

 

It'll all be moot soon anyway.
There's growing use of electronically driven valvetrains, and in the more distant future the internal combustion engine will likely be consigned to history as steam engines are today.




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  # 1780529 13-May-2017 10:32
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Well, happy to admit when I was wrong, I always believed chains were the solution to belts, not sure where I got that information from.

 

 

 

@sidestep are you in Auckland? Do you do Cam Belt replacements on a 2005 Subaru GX 20? If so what would it cost?

 

 

 

I always believed the belt was replaced at 100K or 5 Years whichever was later. 

 

 


 
 
 
 


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  # 1780531 13-May-2017 10:44
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networkn:

 

I always believed the belt was replaced at 100K or 5 Years whichever was later. 

 

 

 

 

 

 

Yes the factory recommends that. I had a different theory & was testing it on my wife's car until she chickened out..

I'm in Canada at the moment. When in NZ I'm located an hour North of Kaitaia, so not in Akld.

 

I'm guessing $1,000 to $1,100 for your cambelt replacement at a quality garage.
Around $500 of that is the parts, including the water pump, tensioner, coolant (rad has to come out).




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  # 1781534 13-May-2017 10:54
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Wow a grand. Won't be doing that prior to sale then. People can buy it and do it themselves :) 


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  # 1781561 13-May-2017 11:19
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For a 2006 legacy it is $1200 parts and labour, I would guess similar to an imprezza.

 

I have always been under the assumption that Subaru engines were difficult to change the cambelt in and that is why they are so expensive? 

 

 

 

 

 

 




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  # 1781563 13-May-2017 11:22
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blackjack17:

 

For a 2006 legacy it is $1200 parts and labour, I would guess similar to an imprezza.

 

I have always been under the assumption that Subaru engines were difficult to change the cambelt in and that is why they are so expensive? 

 

 

 

 

 

 

 

 

 

 

Earlier in the thread someone had said it was easy to access the cambelt on a Subaru because it just required the radiator to be removed. 

 

 


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  # 1781598 13-May-2017 12:29
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networkn:

 

 

 

Earlier in the thread someone had said it was easy to access the cambelt on a Subaru because it just required the radiator to be removed. 

 

 

 

It is 'relatively' easy..

 

Drain the coolant (if the little drain valve doesn't break off)

 

Jack the car up. Remove the under engine plastic tray, remove the radiator hoses (if they aren't stuck on), trans lines then the radiator.

 

Remove the engine accessory drive belts, then remove the crank pulley which occasionally just won't come off.

Remove the plastic timing covers which are often covered in crud.

Set the engine to TDC so you can...

Remove and replace the timing belt, water pump, tensioner, idlers. May as well do cam/crank seals and the  o- ring behind oil pump.

 

Re- assemble in reverse.

 

Fill car with coolant and start up. Make sure car still runs, electric fans still work, thermostat/water pump are working etc..

 

It's not rocket surgery but takes time.. and in a garage time's money.


 
 
 
 


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  # 1781654 13-May-2017 14:35
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Sidestep:

 

<snip>

 

I have a theory those manufacturer recommended replacement intervals are very conservative. But my wife disagreed and wouldn't let it go any longer.

 

<snip>

 

 

 

The depends on the manufacturer. Toyota seem to be conservative but try getting an extra 10,000Km from the belt in a 1980's Peugeot 205 GTI. I know two people who made that mistake.


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  # 1781661 13-May-2017 14:48
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I'll take a timing chain over a cam belt any-time I have the choice.  My next outboard purchase will be Suzuki for that reason.





Mike

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  # 1781669 13-May-2017 15:10
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Suzuki has had its moments. The 2.0l car engine used to be bad for chain guides and tensioner until modified.

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  # 1781807 13-May-2017 22:50
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MikeAqua:

 

I'll take a timing chain over a cam belt any-time I have the choice. 

 

 

But what's your choice if the chain is under-specced and the belt is over specced?

 

 

 

 


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  # 1781823 14-May-2017 02:15
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jpoc:

 

Aredwood:

 

<snip>

 

People choosing cars based solely on belt or chain are stupid. As cam chains can and do fail. Cam chains also stretch as well. And when they do the ECU often starts throwing lots of trouble codes due to the relationship between the signals produced by the crank and cam angle sensors changing.

 

<snip>

 

 

Those are strong words. Calling people stupid just because you do not agree with them.

 

Choosing a car with a chain driven cam over one with a belt driven cam is probably an entirely rational choice.

 

The main reason is one of cost. A typical cam-belt needs to be replaced at intervals of 100,000KMs or 5 years. Most used cars travel around 10,000KMs per year which means that the 5 year period is the one that counts and if $800 is a likely cost for a belt replacement, that means that cam-belt replacement is a bigger cost than third party insurance, road tax or tyre replacement for most people driving a used car in New Zealand.

 

 

 

 

 

 

You are taking my post out of context. There is nothing wrong with considering what the likely future maintenance requirements for a car are likely to be. And cambelt Vs chain is definitely a factor in that. But saying that a car is going to be unreliable or expensive to fix just because it happens to use a cambelt instead of a chain is taking things too far. For example lots of Toyota Corollas use cambelts. And lots of other highly regarded Toyota models also use cambelts.

 

Imagine I told someone considering buying a cambelt Toyota Corolla that they should instead be buying say a camchain Mercedes "because it will be more reliable as it has a camchain instead of a belt" Everyone would jump on me saying that would be silly. Especially as the Merc would most likely use alot more petrol than the Corolla, So overall would cost more to run despite having a Chain. And cambelts are easy and cheap to replace on Corollas. A new cambelt for my 4AF powered Corolla cost the pricey sum of $35 to buy from Repco. And buying a cambelt from a Toyota dealer for a 4AGE didn't cost that much extra. And replacing it took about 2 hours at home. Would have been quicker in a mechanics workshop with access to proper tools and a hoist.

 

And the local Toyota dealer advertises cambelts fitted from $170. Google maps link Yes I have checked and that sign is still there. Note also that you rarely just replace the cambelt only. You often replace the waterpump and belt tensioner as well. And a full timing system service would include replacing the front crankshaft and camshaft oil seals, all of the idlers, and often other parts depending on what car and engine you are looking at. So this is where alot of the cost of replacing a cambelt normally disappears to. And on lots of cars, The cambelt replacement intervals line up with a major service. Which will often mean replacing all fluids and filters as part of that service. And most likely other things that have nothing to do with the cambelt or chain. So even if there is no cambelt, there is often still lots that needs to be done at the 100K service.

 

Also a far bigger thing to consider when looking at reliability for cars with higher kilometres on the clock - Does it have an Automatic gearbox? And if so it it generally a reliable model of gearbox? Or is it known to give problems. As auto gearbox rebuilds are expensive. And if gearbox failure is a common problem, good luck trying to find a known good condition secondhand gearbox that doesn't cost moonbeams.

 

Aredwood:

 

<snip>

 

People choosing cars based solely on belt or chain are stupid. As cam chains can and do fail. Cam chains also stretch as well. And when they do the ECU often starts throwing lots of trouble codes due to the relationship between the signals produced by the crank and cam angle sensors changing.

 

<snip>

 

 

Note that I said "Solely" in my original post. I would hope that someone choosing a new car would at least consider fuel economy and crash safety ratings in addition to "belt or chain" before making their decision. And even better do some Google searches to find out what the common faults are with the model they are considering.

 

Apologies if the word "Stupid" was too strong a word. But I don't see the issue with it as I was not directing it at a particular person. And I most definitely wasn't directing it to the OP. As they already owned the car, And cambelt Vs chain wouldn't have been the main purchasing decider considering they didn't originally know if it had a belt or chain.

 

 






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