Morris Minor Owners Club

I pulled into a petrol station last week and someone chuckled at my car saying 'nice timing chain rattle mate', I was most affronted!

I have noticed that the sound of my engine is quite loud, on idling it almost overpowers the sound of the exhaust if that is any help as a gauge of how loud it is (maybe it is normal?)

I'm thinking therefore I should renew the timing chain, and have noticed 'duplex timing chain' kits on various parts suppliers websites... what is the theory behind upgrading to 'duplex'? Are there discernible benefits?

Cheers,
George

Are you sure that it is the timing chain and not something else rattling? I find that passing comments from strangers diagnosing mechanical problems are not always correct . This thread might be useful. Some on here feel there is no need for a duplex kit but others do:

http://www.mmoc.org.uk/index.php?name=P ... ght=duplex

Hi Louise, I'm not certain infact, but having looked at the video linked in that thread showing the timing chain slack, I will remove the cover and inspect to see if it is this rattling and then go from there.

Thanks for the link, George

Duplex is for high spring pressure - and high lift cam. For quietness - do what Rover did - fit a tensioner! Either bag the whole kit off a scrap Mini - or buy new parts from the likes of Minispares or Minisport. You will need a new chain + new small pulley + cover with bulge (and gasket) and the tensioner assembly. Easy fit - one small hole has to be blind drilled to about 1/4" depth to take the pivot shaft for the tensioner.

I cut my teeth on a 948 and rebuilt it using the same single timing chain and rubber rings in the camshaft gear. I didn't know any better at the time. Well the chain was slapping the side of the cover but would reliably stop at 28mph. The load on the engine at that point was enough to keep the chain tight enough to stop hitting the cover. I can be excused due to my age but both my father and his older brother who had been wrenching from the 1920's thought it was a connecting rod bearing. I had the oil pan off numerous times to gauge the bearings until I put something to the timing chain cover to listen.

If only to be devils advocate, I'll put forward the case, as I see it, for the duplex set up.

You can get it from Minor parts suppliers not breakers yards.

There are less parts to change.

There is less "engineering" required, countersink existing holes rather than drill a new blind hole.

The wearing surfaces are doubled which in effect means the oil film is maintained and the wear is negligible.

I've got no idea who thought the original "rubber band" system was a good solution to chain wear but I trust he was an accountant and not an engineer.

I find the idea of metal constantly rubbing against rubber, even with an oil film "not right" somehow.

By all means fit Duplex - but it will soon be rattling too! The single hole to be drilled is dead easy - and since it doesn't go through - there is no risk of swarf going in the engine. The countersinking is not so easy - a normal drill bit does not have the correct angle - a proper countersink is necessary - and they must be deep enough to make the heads of the new screws flush to the plate. There is of course also a timing belt drive arrangement available - said to be very quiet and very accurate with the cam timing. I had one on an engine I bought - didn't fancy it - sold it on for almost as much as I paid for the excellent engine !

It might be easy for you but where does the blind hole go and what happens if it goes a little wrong?
For the Duplex you need a countersink bit, not a drill.
But you have a pilot hole already in the perfect position, it might take a couple of goes to counter sink enough, but it would be hard to go wrong or get in a situation where you are snookered with a hole in the wrong place that attracts your drill bit like a black hole.

Grease on the drill bit and a magnetised screwdriver will see off any swarf.

How about some actual experience from other members?

I quite agree! Have done both several times. The tensioner is the one that stays quiet - and the single small hole is VERY obvious - can't go wrong! It also gives option of another breather for the engine - on the timing cover -which can't be a bad thing. It's personal choice - but for a non hairy cam/non super strong valve springs - I suggest the simplex with tensioner is the better arrangement.
http://www.minispares.com/Product.aspx? ... 06%20PIECE...
Also need a cover - http://www.minispares.com/Product.aspx? ... %20BREATHE...
This one has no extra breather - but breather ones are available too!

Nothing "can't go wrong!" if only, I'd be out of a job.
Haven't you heard of Murphy's law?

Really - with this - it can't!

That isn't helping.
How about X marks the spot?
I'd opine that the duplex set up "can't go wrong".
But I'm too old and too cynical to believe it.
Some of my favourite last words are "what could possibly go wrong" as uttered by several winners of the Darwin awards .

The tensioner mount bolts on under a set screw - the hole for the pivot is clear and is marked through with a scribe. Remove the tensioner - drill the hole - refit tensioner this time with the swivel pin fitted in the hole - job done!
The duplex set can go wrong - some Mini lads 'forget' to countersink the holes - or don't get the screws in tightly enough (screwdriver is NOT enough) and they work out and jam the chain! Some Duplex chains have joining links (which protrude slightly) - if fitted wrong way round they catch on the screw heads - and ruin the chain (and possibly the engine if it's not stopped quickly enough!) - and, the camshaft sprocket being thicker than before is prone to rub on the casing - enough to wear a hole/slot in the casing!! All unlikely - but all have happened in recent times on various Mini forums.

Sorry BMC but what is a scribe?
Will a ballpoint or a pencil do? I've got them.
Does it matter if this scribe isn't at 90 degrees to the back plate?
Would I be better off with the front panel and rad removed or could I get away without?
Is a circle OK or does X need to mark the spot?
It's easy with some engineering nous or maybe just common sense but that doesn't actually mean it's easy from a standing start.

How many thou out before the before the tensioner binds up and does nothing useful?

Keep it simples - get a like for like replacement kit don't bother with duplex. The rubber tensioners on the single row chain make it so quiet when you restart the engine it's a joy. As someone else has said duplex chains will rattle in due course in any case. Regards, John

MarkyB - I can only lead the horse to the trough - I can't make it drink! It's NOT critical - it works.
Yes new simplex chain and rubber bands will last - for a while. A little while !

GAH! if the adverts say things are "simples" in an amusing way it must be true.
The pleasure of having a quiet timing chain turns into the disappointment of it rattling again because it was under engineered just as fast, if not sooner, than it did when the car was new.

I'm not advocating the simplex set up. Where have I said that?

What I'm saying is that what seems "simples" to us isn't actually that simple in practice.

If you have no background and just dive in with the tools you have to hand and the "knowledge" that it is a simple job from here, what could go possibly go wrong?

How would you fell if you were leading a horse up a garden path that led to a certain creek paddleless? to mix a few metaphors?

Maybe I'm extra cynical tonight but I'm doing computer support now, and have to deal with things like a PC that won't boot up because the user deleted files during a "tidy up" because they didn't know what they were for.

I'm afraid I wondered if they would open the bonnet of their car and pull out whatever stuff they didn't understand .

There is always scope for things to go wrong and it needs to be acknowledged, not brushed off.

Oh - that's why my computer isn't working correctly!!!
In my experience - there's more to go wrong with fitting duplex - and it's not as quiet as the tensioner/simplex solution. Obviously MG Rover thought so too! Each to their own.

I'd go for simplex and tensioner.
Simplex chain isn't under-engineered for the job- many, many other manufacturers used it. It's the lack of tensioning which is underengineered by todays standards! In years gone by lots of things were done which would be considered likewise in our over-enlightened modern times in which we live in. Duplex chain without a tensioner is hardly a scientific solution! Duplex will stretch, and rattle, and draw more of your hard fought for horses away from the wheels, and draw a fair bit of hard fought for dosh from your pocket in doing so. A raid on a lateish Mini/Metro at your local breakers will also give you a practise run at dismantling the timing case etc, and furnish you with a crank damper "in the price" in all probability