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[The Sheriff]

More to the point why are there not more 'safe' engines so that if the belt does go there's no meeting of valves and pistons?

Long ago in the mists of time, I asked Mr DTM this very question. Interference engine v non-interference. He explained the answer in great detail. Wish I could remember........


It was something to do with power and efficiency.

Edit: i must read all posts before replying. Sorry Aaron.

[Field Marshal Dr. Opti]

More to the point why are there not more 'safe' engines so that if the belt does go there's no meeting of valves and pistons?

Because you don't get efficiency by building in safety - non interference would mean low compression or inefficient combustion chambers with heavily pocketed pistons etc, and modern engines are pretty much on the ragged edge of what the designers can get away with in the name of fuel economy and saving the environment..

Is this why my 1974 Capri 1600 OHC survived cambelt failure?

Truth be known it was a bit of a lorry.

[Andy B]

More to the point why are there not more 'safe' engines so that if the belt does go there's no meeting of valves and pistons?

Because you don't get efficiency by building in safety - non interference would mean low compression or inefficient combustion chambers with heavily pocketed pistons etc, and modern engines are pretty much on the ragged edge of what the designers can get away with in the name of fuel economy and saving the environment..

Is this why my 1974 Capri 1600 OHC survived cambelt failure?

Truth be known it was a bit of a lorry.

Yes. The Pinto engine was a safe engine.

[BazaJT]

Thought the 1600 OHC-presume you mean the pinto motor?-was an interference type and would survive depending on how hard engine was trying at time of failure and/or how lucky you were.

[Nick W]

Is this why my 1974 Capri 1600 OHC survived cambelt failure?

Yes. The Pinto engine was a safe engine.

2.0l Pintos are safe; I've refitted belts at the side of the road.  1.6l aren't, due to differences in the cylinderhead and valve lengths, although you might get away with it. You can bolt a 1.6l head onto a 2.0l engine but it won't run. I'm sure you can guess how I discovered that.


As for chain or belt, there are good and bad of both. Modern chains tend to be more problematic than older ones for a number of reasons: they're much longer; they tend to be noticably smaller; they are much more highly stressed compared to the short chains in OHV engines; oil change intervals are much longer, and the tensioners really don't appreciate that. But there are some bad chain installations: Mini(etc) A-series engines use a rubber coated flap to tension the belt, and slack/noisy chains are a common problem as a result; Micra engines and 2.0l diesel BMW engines are well-known for expensive chain issues(largely due to someone fitting it at the back of the engine). Good ones are excellent though, a robust chain with a heavyduty tensioner will last the life of the engine even on DOHCs; check out the cam chain rattle on an XK, Merc I6 or Rootes 4. You will need good hearing!

[Andy B]

2.0l Pintos are safe; I've refitted belts at the side of the road.  1.6l aren't, ....

It was a very long time ago now but I wound the crank round on my 1600 with the cam & followers fitted. Nothing fouled

[Magwheels]

Bring on electric power......None of the above to worry about......just whether you will have enough juice to get there!

Or back!

[Field Marshal Dr. Opti]

Hydrogen fuel cell is the way to go.

Once teleportation is invented we won't need to worry about the price of fuel.

[TheBoy]

Belts don't stretch, chains do. Doesn't matter how good a tensioner is, the valve timing will be out.

[The Sheriff]

Hydrogen fuel cell is the way to go.

Once teleportation is invented we won't need to worry about the price of fuel.

No, but British teleportation will charge a fortune for their services. Nothing ever changes, Opti.

[dbug]

Belts don't stretch, chains do. Doesn't matter how good a tensioner is, the valve timing will be out.

You sure - elastomer based

[Vamps]

Well the Honda is a chain, apparently.............

[05omegav6]

Belts don't stretch, chains do. Doesn't matter how good a tensioner is, the valve timing will be out.

You sure - elastomer based

Chains 'stretch' as a side effect of wear, belts are effectively stretched by the tensioner

[Marks DTM Calib]

The Rover (Buick) v8 was best, chain, no tensioner, never rattled and never failed in normal use.

Er, it never failed but, stretched badly and wore the gears so the cam timing goes a mile out. Hence why you can by beefed up replacement duplex chain sets for them.

Things to consider

1) Modern engines are not simple push rod units with the single cam close to the crank

2) Chains do stretch (despite oil changes etc)

3) Chain guides do wear (also despite oil changes)

4) Adjuster oil feeds can clog (as many are pressurised like a cam follower).

So my personal preference is a cam belt and workings, this is due to me keeping cars for high mileage and I am quit happy to change a belt and know its done and good, chains fail, that's a fact and they can be an absolute shit to change (ask a BMW 2.0 diesel driver......)

[Marks DTM Calib]

Belts don't stretch, chains do. Doesn't matter how good a tensioner is, the valve timing will be out.

You sure - elastomer based

No they don't generally as they might well be a rubber external coat but inside they have a Kevlar or nylon re-enforcing