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[theolodian]

As James said,

James hasn't posted on this thread - he is outside cleaning out the car    

Who is James & why has he not posted anything??

His arms are too sore.  Cambelts and bruises from SWMBO.  

[brett1408]

oooooh ! big mistake assuming a chain will never break, i had one go on a 16 valve merc 190, it were'nt cheap ! old skool v enginge's are the safest in this aspect i suppose, no chain or belt but 2 gears running directly off each other, rover v8, ford essex and so on,  i remember reading somewhere that it was fiat who invented the timing belt, not sure though anyone know ?

[Pitchfork]

As James said,

James hasn't posted on this thread - he is outside cleaning out the car    

Who is James & why has he not posted anything??

His arms are too sore.  Cambelts and bruises from SWMBO.  

So are mine - 4 hours of playing Melodeon last night for a Ceilidh!

[Pitchfork]

oooooh ! big mistake assuming a chain will never break, i had one go on a 16 valve merc 190, it were'nt cheap ! old skool v enginge's are the safest in this aspect i suppose, no chain or belt but 2 gears running directly off each other, rover v8, ford essex and so on,  i remember reading somewhere that it was fiat who invented the timing belt, not sure though anyone know ?

Depends on whether it is driven sensibly I suppose! :-?

[jemis]

In the past I've had a few carlton gsi's and a senator all with timing chains and all I can say is 12 valve works 24 valve doesn't. and just like when the cambelt goes the engine's going to its grave.

[brett1408]

oooooh ! big mistake assuming a chain will never break, i had one go on a 16 valve merc 190, it were'nt cheap ! old skool v enginge's are the safest in this aspect i suppose, no chain or belt but 2 gears running directly off each other, rover v8, ford essex and so on,  i remember reading somewhere that it was fiat who invented the timing belt, not sure though anyone know ?

Depends on whether it is driven sensibly I suppose! :-?

        hehe, it was'nt being  

[waspy]

Before my Mig i had a Rover 800 Diesel & that runs a very reliable VM engine, no belt, no chain, just cogs= nothing to change, snap or pull.
If the Rover was easier to get parts for i wouldn't have changed, but i do love my Miggy just as much even though down on power compared to the Rover.

[theolodian]

oooooh ! big mistake assuming a chain will never break, i had one go on a 16 valve merc 190, it were'nt cheap ! old skool v enginge's are the safest in this aspect i suppose, no chain or belt but 2 gears running directly off each other, rover v8, ford essex and so on,  i remember reading somewhere that it was fiat who invented the timing belt, not sure though anyone know ?

Depends on whether it is driven sensibly I suppose! :-?

What, like idling while parked?  :-?

[Ken T]

I never recall having seen a failure of an engine in a Motor cycle or Car, failing because of a push-rod problem or failure!
So - why do we now have over-head camshafts, & perhaps
more critically, camshafts driven by rubber-bands?
Seems to me that if you do have to have OHC, that chain driven are more reliable/ economical to maintain (e.g. Traktors, Nissan Micras) than these wretched belt-driven lumps (unless of course they provide a good excuse for a Beery weekend get-together for readers of the ultra-right Daily Mail!)
Discuss :-?

Micra's are well known for breaking the chain, and just generally wearing out the chain and tensioner system soon. Nissan claimed it was because the oil wasn't being changed enough, but....... I guess like all systems, it depends who's designing/making it.

Ken

P.S., its a pain to change the chain or tensioners on the micra.

[Marks DTM Calib]

Its a mith this chain super reliabilty thing, there not, they streth and wear (as you would expect).

I ahev known quite a few of the 6 cylidner diseasels to suffer chain problems, on these the tensioner normlay wears and the pump umps a tooth.

And the driver behind over head cam, performance.

To get good high rev ability you need to be able to have a controlled valve opening AND closing.....and by having an over head cam you have a light valve train which gives you this.

Compare this to a puch rod where you have possibly a hydraulic follower (although some dont), push rod, rocker, valve....to get good high rev ability you end up fitting big valve springs to shut the valves fast and all because you have a large mass of valve train to move!

Now, thats a very small reason why!

My personal preference is for a belt as they are quiet and because you service them regulalry, they are a known item where as chains are very much unknown....

Gm however, are moving there engines back to chain setups....

[TheBoy]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.

Cambelts, on a plus point, are MUCH easier to replace than a timing chain (which pushrod engines also have!)... and cambelts are also reliable if changed on schedule.

Given all the pro's and cons, I would rather change a rubber belt every 40k miles, than have to struggle to do a timing chain every 100k....
 

The question was rhetorical (& I was not anticipating serious answers)
But in answer to your point, who ever needs to change a timing chain apart from those who patently ignore servicing schedules to the point of crass negligence, & would not the same people cheerfully miss the recommended cam-belt change intervals too?

Yep probably very true.

Chains are known to stretch over time and the guides tend to break up around 100K.

Poll?  How many Traktor owners on the forum have had to replace a timing chain?
I'm at 140K currently

Remember, poor oil servicing accelerates the wear on the chain, so keep to those 3k oil changes!

The likely value of car and the huge amount of labour (head off, sump off (which I think may mean engine out)) means the car gets written off instead....

[Martin_1962]

Its a mith this chain super reliabilty thing, there not, they streth and wear (as you would expect).

I ahev known quite a few of the 6 cylidner diseasels to suffer chain problems, on these the tensioner normlay wears and the pump umps a tooth.

And the driver behind over head cam, performance.

To get good high rev ability you need to be able to have a controlled valve opening AND closing.....and by having an over head cam you have a light valve train which gives you this.

Compare this to a puch rod where you have possibly a hydraulic follower (although some dont), push rod, rocker, valve....to get good high rev ability you end up fitting big valve springs to shut the valves fast and all because you have a large mass of valve train to move!

Now, thats a very small reason why!

My personal preference is for a belt as they are quiet and because you service them regulalry, they are a known item where as chains are very much unknown....

Gm however, are moving there engines back to chain setups....

You can have cams high in block with short push rods.

I have had a pushrod car engine up over 7200 rpm and it came off cam

[Marks DTM Calib]

Its a mith this chain super reliabilty thing, there not, they streth and wear (as you would expect).

I ahev known quite a few of the 6 cylidner diseasels to suffer chain problems, on these the tensioner normlay wears and the pump umps a tooth.

And the driver behind over head cam, performance.

To get good high rev ability you need to be able to have a controlled valve opening AND closing.....and by having an over head cam you have a light valve train which gives you this.

Compare this to a puch rod where you have possibly a hydraulic follower (although some dont), push rod, rocker, valve....to get good high rev ability you end up fitting big valve springs to shut the valves fast and all because you have a large mass of valve train to move!

Now, thats a very small reason why!

My personal preference is for a belt as they are quiet and because you service them regulalry, they are a known item where as chains are very much unknown....

Gm however, are moving there engines back to chain setups....

You can have cams high in block with short push rods.

I have had a pushrod car engine up over 7200 rpm and it came off cam

Never said you couldn't, but, you need big springs and that adds strain and high wear rates. On a push rod you idealy wouldn't run high lift cams, you would use the rocker to get your gain.

You also end up running multiple springs in order to overcome resonance issues to!

[Martin_1962]

It was running a Kent fast road cam, yes there was multiplication from the rockers, but the head did also have a 60 thou skim.

I met one chap who used to run to 8000rpm

And anything above poverty spec had twin valve springs.

My only problem was I reved a pool car with a long stroke 1300 to valve bounce thinking little engine - plenty of revs - not realising it was alot longer than my old 1600.

I just wish I had a die grinder - grinder bits in a drill in my bedsit was quite awkwards

[Ford Prefect]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.
 

Rubish I am afraid... Take a look and the old bristol engine as used in the AC Ace before Carol Shelby molested it.

OHC engines main reason in racing is to reduce the reciprocating masses, there are no push rods or rockers to accelerate/decellerate on each cycle, as for the production engine this can't hurt, but the OHC design also significantly reduces the number of parts that need to be made and thus makes the engine cheaper to build. Hoever and SOHC design either has to have the valves all in a row (like the 8V engine) which is not so good for gas flow, ideally you want inlet and exhaust valves each side of the head, this can be done, but you can either add a set of rockers, as BMW and Triumph did (truimphs version being as woudl be expected a far more elegant solution!) or add a second cam.

Stewart