timing chain or cambelt

[v6hughes]

which do you think is best / you'd prefer alfa's to have

[Mitch166]

You must be really bored this evening

[10,500RPM]

Timing chain. My old DOHC sierra had one, it meant I could buy a secondhand waterpump (ran off the aux belt) for £10 and fit it myself. How many Alfa owners can say that?

[v6hughes]

Originally Posted by Mitch166

You must be really bored this evening

yep

[symon]

Cambelt.

Quieter, more efficient, more accurate control of timing (don't get longer as they age), cheaper to make, require no lubrication.

And generally much much easier to change.

In an ideal world all cars would have gear driven cams though.

[andyalfagtv]

Originally Posted by symonh

Cambelt.

Quieter, more efficient, more accurate control of timing (don't get longer as they age), cheaper to make, require no lubrication.

And generally much much easier to change.

In an ideal world all cars would have gear driven cams though.

Desmodromic valve gear would be great in cars. I am sure that eventually the gears would wear out, but it would take a long time, and they are engineering works of art.

[symon]

Originally Posted by andyalfagtv

Desmodromic valve gear would be great in cars. I am sure that eventually the gears would wear out, but it would take a long time, and they are engineering works of art.

I think it is great too, however how would you engineer in variable valve timing?

Then there is the wear/clearance issues you mentioned.


When I suggested gear driven cams I was thinking of just replacing the belt/chain with them and keeping the cams and springs. It has been done on OHV engines like the Ford Essex V6. So after all of these years why couldn't someone come up with a solution for OHC engines?

[mudhut]

Belt every time for the reasons symonh says. My Alfa engine's water pump is driven by the aux belt - thought they all were. Changing the water pump for £10: in my dreams.

Desmo valve gear isn't dependant upon the method by which the cams are driven. It refers to the mechanical arrangement for closing the valves (thus not relying on hefty springs). The old Ducatis used hairpin valve springs to hold them closed lightly.

Using bevel gears to drive the cam like the Desmo Ducatis has its own set of problems. Also expensive, like the Inter Norton and K series Velocette and others decades before them.

P.S. Cam belts do at least keep people in employment. Oh, and chains break too, ask plenty of GM 2.2 litre engine owners (Z22 engine I think it's called) - we aren't talking new valves here but new c/head. Ask me how I know.

[keithyboy]

Interesting.

The Essex V6 had fibre timing wheels which were given to disintegrating and taking the engine with them. My old Primera had a chain and at 140,000 miles+ made no noise whatsoever. The chain on my Mini rattled like a biscuit tin full of nuts and bolts and 50,000 miles. I've had 2 DOHC Sierras and they were OK too but they can let go without warning at around the 100k mark. There is also an issue with them in that if the oil is changed and you start the engine without building the pressure first, the chain can slip a tooth or two as the tensioner works on oil pressure.

When it comes to belts, a change for my Alfa is approx £250. By the time I've bought the parts and the kit, doing it for myself hardly saves anything. The job on our Volvo was £175 but only needs doing at 60k (but that includes a reasonable safety margin). The old Mondeo Zetec we had had an 100,000 mile timing belt interval and they don't have a reputation for going early either. changing the belt on a CVH powered Ford took about an hour tops.

I think the answer is that I really don't give a toss which it has as long as it's engineered properly. I'm not entirely convinced that the TS one is to be honest.

[Pte1643]

Originally Posted by keithyboy

changing the belt on a CVH powered Ford took about an hour tops.

Both of the Fiestas I had, had the 1.4 CVH engine.

Changed both of the belts myself, with a little help from the haynes manual.

Took a little longer than an hour, not much more if I recall, I have a reasonable amount of mechanical "Nouse", but I'm no mechanic.

Easy little number on the CVH.

[Ralf S.]

Aye! It doesn't matter which, as long as it's reliable.

I'd have gear driven cams though, if I was designing an engine myself.


Ralf S.

[156Chris]

+1 for the CVH the cambelt (on my sierra) was nicely positioned at the front of the car with lots of space to work ... don't remember any scraped knuckles from those days