Clementine's Garage
Clementine the Cat
 
Image of flower
Yellow R4
 
home my cars restoration tech tips guides forum
Réparateur d'automobiles

If the timing chain break down...

Leonardo.IT

Leonardo.IT

Enthusiast
Messages
255
Location
Tuscany (Italy)
Are the valves safe?
My car had this failure about a week ago while I was travelling to Wales, it's near Lyon and I need to bring it back in Italy, one of the possible ways is to change the chain there and let it drive home.
I know for sure that some engines don't suffer head damage from a chain break.
Is the 956cc Cleòn one of those?
 
Timing chain failure is rare but will involve engine and gearbox removal
In the only 2 cases ive come across in 40 years one car was fine the other bent some pushrods
Because the valves run vertical in the head a piston coming up meeting a valve in the way will force it close level with the top of block possibly bending pushrod if rocker arm is trying yo go down st the time of failure
It Is more likely to have slipped round a few teeth if tensioner has let go and just out of time and no bent pushrods
Easy to take valve cover off now and quick look
 
New pushrod are easy to find and quite cheap... I've seen Melun sells them... think you can easily buy and have them delivered directly by the mechanic shop. ..
 
Giving this further thoughts as you mentioned it being 956cc engine this engine is extremely rare in UK and only fitted 1972 to 1978 in renault 5tl versions
Reason I am now worried is the 956 has got stepped pistons meaning IF the valves make contact with a raised section which protrudes above the top face of the block at tdc it is not a flat level piston meaning the valve COULD GET BENT as it is not an even contact area meaning it may not transfer force vertically to the valve and then the weaker pushrod
Sorry but I've now rethought the odds to being 50/50
Maybe Angel will have some further thoughts
Shame mention his name in post not same effect as tagging does using facebook ☺
Hoping for the best
 
The engines in which piston would collide with open valve in case of chain/belt failure are called "collision engines" here in Poland. Non collision engines are less common I think.
 
Yes agreed with above but they are only listed as likely to do damage
Doesn't normally go into more details and as this is a rare event on R4 maybe less well documented
Reason for chain wearing is because alternator and waterpump is driven from other end of engine via camshaft
Gordini Alpine and power steer R5tx models use twin duplex chain for longer life
Older renaults 8 10 12 18tl volvo 343 etc are fine as crank pulley drives ancillaries
New 5 9 11 clio etc are transverse and also crank driven
 
Unfortunately I'm any near to the car, I had to leave it in Roanne, about 60 miles nort-west of Lyon, and continue the travel as I was attended in Wales for a work.
I think that at the first time the chain jumped some teeths, but I tought it was another kind of problem, that's why I continued to work on it until, when I was trying to start it, the camshaft stopped moving.
I didn't hear any sound, so I really think that the chain isn't broke, but there is no connection between the crankshaft and the camshaft.
I'm asking about the type of the engine (collision or not, thank you chudson I didn't know how to call them) because I know that there are some engine like the older FIRE Fiat ones (80s engine, earlier than our Cleons) that are non-collision and I've heard any collision sound once the chain has stopped working.
In one case I'll ask to the garage where the car is to replace the chain, in the other is going to be a little harder.
 
Nice to se you're already so used to imperial measures. ..
By the way, I think the Cleon engines are a bit older than Fire ones.
 
Yes, I know that FIREs are quite newer than our Cleons, but since non-collision engines were quite more common in the past, I hoped that our was one of these...
 
I've had two 845cc machines break a valve chain.

Neither was damaged. New chain and tensioner and away you go.

I believe this is because the 845cc engine is "long stroke", i.e. the cylinder is long and narrow, and so even with the piston at top dead centre it still clears the open valve.

But I couldn't say if the same would apply to a 956cc engine as the clearance between the cylinder head and piston top may be less. Depends on the bore/stroke characteristics.
 
My understanding is that both engines are non-interference (non-collision) and that the valves don't open far enough to reach the pistons when they are at the top of their stroke.
Of course, if the engine's been modified, like shaving a big chunk off the head, it could be a different matter.
 
Been trying hard to find a picture of a 956 piston which is quite different in having a raised stepped crown which protrudes into the combustion chamber at tdc
This is the only version of the c type engine that doesn't have flat top pistons hence my concern if you re read my earlier post
Don't forget all info I can find on interference engines is based on engines fitted with rubber cam belts virtually standard across manufacturer since the 90s
 
I'm going to take the car back in Italy as it is, when I'll come back too I'll check this whole thing and I'll write it down here, hope it will be useful for someone else and nobody is going to need it.
 
Remembered that few months back richard birchenough had a disaster with blanche
Also a 956 savane model he dropped a washer down the carburettor
He took the head off to investigate and took some pics which I have borrowed one to illustrate the stepped pistons downloadfile.jpeg
 
mmmm....

Engines fitted with rubber cam-belts virtually standard across manufacture since the 90's

Does my 956cc fit in the above category? First registered April 1990. Obviously, produced sometime prior to that.
Looking at the engine, is there anything obvious, that would tell me if it has belt or chain driven timing mechanism?

Very responsive little power unit BTW

Cheers
 
Neil
I think you may have misread my post or you are trying to get me to type even more content just because I threatened to cut it down
My comment referred to newly developed engines ie the Energy engine from renault never fitted to a renault 4 !
We have already established all R4 engines are dinosaur designs using pushrods and non crossflow ports

Early ohc engines such as ford pinto cortina1972 and vauxhall Victor fd 1970 were all belt driven
As emissions were supposed to go down on newer engines and power outputs went up the valve to piston clearances got closer and closer on each manufacturers NEWLY designed engine

Meaning by mid 90s with all cars needing catalytic convertor to meet emission laws overhead cam engines with rubber belts were normal

I am sure people have retrofitted clio energy engines to R4 but
If most car owners don't get belts changed at correct intervals they are hardly likely to want to remove engine to get it changed on R4
Changing emission laws are one reason old cars got phased out if you had ever looked under the bonnet of retrofit US spec Renault 5 le car you would see how awkward that is to work on also gives less power and more fuel consumption

Right that's it no more from me on this subject
 
I disassembled the engine and... bad news, the 956 Cleon is a collision engine, so the valves can touch the pistons
IMG_20160106_114412902 - Copia.jpg
IMG_20160106_130603572_HDR.jpg
 
Another point against the small cleon engine. It seems really pointless in the r4 gamma, I really do not understand why it was chosen to be the only one in the latter italian exportations.
 
You must log in or register to reply here.
Community platform by XenForo® © 2010-2025 XenForo Ltd.
Back
Top