Timing belts -- another general query - The Growler
We read frequently the importance of changing these, the critical intervals for doing so, the dire consequences that may happen otherwise, and the vital need to check whether a prospective purchase has had this done. Most every car brand seems to be involved. Apocalyptic finger-wagging in these columns reminds us remorselessly.

My idiot question is for heaven's sake in this day and age why hasn't anyone come up with something better than a belt, failure of which can ruin an engine?
Or at least belts which are a bit more up to the job? Whatever happened to timing chains? I grant they could break but would give plenty of warning. The other thing is why are the belts (appaently) so puny they don't last very long on engines which otherwise do high mileages on their other parts? My Harley Davidson Evo has a drive belt good enough to send a lot of heavy horses to the rear wheel. Unlike a timing belt which is more driven than driving (!) The HD belt drive is known as the best in the business -- I have never heard of a belt failure on huge mileage engines, yet the thing is out in the weather and does all the work.

I await a flood of enlightenment from our experts.
Re: Timing belts -- another general query - Dan J
Go back to pushrod engines, that's what I say...
Re: Timing belts -- another general query - Dave
Dan J wrote:
>
> Go back to pushrod engines, that's what I say...

As long as they had hydrolic self adjusting clearences I don't see the problem with OHV.

Not so much fun doing valve clearences every 5k though!

My skoda was great! The valves must have been self adjusting 'cos the went 45k without problem.
Re: Timing belts -- another general query - j jones
Cheaper to build in the first place. Cheaper to maintain, if done according to makers specs. Much less noisy than timing chains.

I see the new Ford Duratec engines have metal quasi-chain cam drives.
Re: Timing belts -- another general query - Andy P
I've seen a new engine design recently (from Saab I think), in which the valves are driven by individual actuators (they were either hydraulically or electromagnetically operated). This did away with the timing belt altogether.


Andy
Re: Timing belts -- another general query - Bob Jeffery
Or why don't manufacturers at least come up with an efficient engine design whereby the pistons don't collide with the valves when the belt finally (or prematurely) expires? It wouldn't be such a big issue then.
Re: Timing belts -- another general query - David W
Bob,

In modern diesels there is virtully no combustion chamber space with the piston at TDC, hardly room for a bit paper between piston and valves. Only needs the valves to stay down a few mm and disaster.

They would have to re-think the valve design and come up with something like a rotary valve, one that didn't enter the combustion chamber anyway.

I'm happy with timing belts overall, never had one break apart from one guy years ago who thought he was beating the system not bothering with maintenance, TD Ford and the head "exploded" when the belt went at a cost of over £700. System beat him that time.

If you take notice of HJs advice on changing belts and ensure your dealer/independent is aware of any tensioner issues surrounding your own car then belt failure is unlikely.

David
Re: Timing belts -- another general query - ROBIN
I must say that I cannot quite see the point of twincam diesel engines.
5000 rpm is hardly going to cause valve flutter with any likely level of mechanical inertia.
Even if it did, pushrods and rockers dont have to be heavy because they are crude.
Re: Timing belts -- another general query - Stu
Growled: "My idiot question is for heaven's sake in this day and age why hasn't anyone come up with something better than a belt, failure of which can ruin an engine?"

I bet if the space shuttle required one they'd make them very reliable PDQ, but cars ... no political value.
Re: Timing belts -- another general query - THe Growler
I guess your weary cynicism answers my question!!
Diesel Engines - David Lacey
In an answer to Robin's point, above:

The point of twin cam diesel engines is to be able to position the inlet & exhaust valves in the best position for volumetric efficiency. Without twin camshafts, this would not be possible.

David
Re: Diesel Engines - Andy P
Just on the subject of twin-cam 16V engines, are Honda the only manufacturer to make single-cam 16V engines?

If so, why?


Andy
 

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