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Discussion Starter #1
Hello everyone,

My name is Enrique(Spanish is my first language so some of the technical names might be a bit off, I'm sorry) , I'm currently fixing my Renault Clio 1.6V with my dad because the timing belt broke and some of the valves got bent sadly.

We took off everything, the timing belt, the cylinder head, replaced the bent valves, cleaned out the cylinder head, bought the things we need to put it back together but we have encountered a problem.

We put in the new head gasket and laid the Cylinder head on top of it, we replaced the bolts because one had stretched. We replaced them with 10.9 16mm bolts which don't have the same length of thread the original ones did, but maybe like half of the thread (is that okay?)

We bought a torque wrench and we proceeded to start tightening the bolts(following the instructions of 15ft-lb and 240 degrees afterwards) in the correct sequence(snakelike pattern) but we have stumbled onto a problem, after following the instructions, we see that the bolts all have different torques and I'm not sure but it doesn't make sense to me that they don't all reach similar torques.Some have 60ft-lb, some 50, some 55, and one cant even reach 50, it stays at 48, we tried giving that one a little more but we gave it almost half a turn more and it stays at 48ft-lb. We're not sure how to proceed because we don't want the car to break again. Please help and thank you in advance.

PS. if we untighten the bolts, does the head gasket get damaged? do we have to replace it?
 

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Where did you get the new bolts? Looks like they are the wrong type. The head bolts are special stretch-type bolts.

Ideally you can only compress a new head gasket once but it may be worth fitting the correct bolts and see what happens. The only problem being that should the gasket fail you will not only have to replace it but also the bolts. The bolts are a use-once-only fitting.
 

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One of the reasons for turn to angle "torque" settings is that it creates a known "stretch" and hence load.
Setting to traditional torque readings can give different internal stress in the bolts as friction on the thread surfaces can significantly affect the effort to turn.
If I recall correctly the difference between torque on a dry bolt can be 30% higher then the same torque (against rotation) for a lubricated bolt.
Easy enough to understand if you remember how tight a dirty bolt can be compared to a clean one that spins in with fingers.

So no, I would be surprised if torques on a traditional torque wrench came out the same on every bolt for the same angle rotation and not worry at all that they are different.

On 10.9 bolts (A subject I've been researching for my own use)
Most head bolts seem to be 10.9 or 12.9, 10.9 being the most common as far as I can find.
So as long as unthreaded bit is same diameter as the bolts you took out I would not panic too much.
Some manufacturers reduce the diameter from standard bolts so this will effect the joint mechanics.
In effect the bolt is working as a spring and a different size will create a different "spring" load.

I would be concerned on the length of thread.
If shorter there is more load per thread and so more chance of the cylinder block thread failing or stretching slightly... which will cause the head gasket to fail and may strip the threads. Possibly scrapping the block.

For that reason if no other I would replace the bolts with the proper ones from Renault.
For the cost of the gasket, I'd change that as well even though not used as such.
The work involved in a gasket change is too great to risk a failure in modern cars.

Old cars I've slapped on a bit of red fibre sheet with the relevant holes knocked out but those days have gone long ago.
 

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Discussion Starter #4
Thank you Dancingdad and madnoel10 for the replies.

About the bolts, we measured the height of the cylinder head and how much thread goes into the block below(it's called carter in spanish, I'm not sure about the name in english) and the thread on this new bolt(which is also used for cylinder heads) and the thread was more than enough, the thread is on a little bit less than half of the bolt(is that ok?)

The bolt is exactly the same as the original ones that came with the car, except that it has an hexagonal head not the tor head and the thread only covers half of the bolt, not almost all of it like the original one. the diameter is the same. We had to change the bolts that originally came with the car because the length had exceeded the 117.7mm.

We're a little tight on money so we try to save some everywhere we can.
So it's okay that the torques are different on every bolt after doing the 240 degree turn?(ranging from 48 pound-ft to 60 pound-ft)
We should also buy a new head gasket just to stay on the safe side?

Thank you very much in advance.
 

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You just can't use any bolt even if it from another engine. The bolts are specially designed and manufactured from specially formulated steel (to allow for stretch and tension). Think of them as super elastic bands which when stretched provide not only tension but also strength to the engine structure.

Plus the threads are rolled and not cut and should not be cut or modified in any way.. The bolts are specific to each engine type and not universal.

I appreciate you are trying to reduce costs but if the bolts fail to do their job correctly you could end up with total engine failure. There are some jobs on cars where you just can't cut corners without risks.
 

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Not going to argue against Noel as using the proper bolts is the only correct answer we can be certain of.

However, googling 10.9 head gasket bolts brings up some interesting information to enable you to make your own decision.

I'm sure that what you have done is not "by the book" that is to Renault Specs.
I'm not sure that what you have done is wrong but cannot say it is right either.

I am certain that getting different torque readings (within reason) from different bolts with same angle turn is nothing to worry on.
And if thread engagement in the hole is the same, that is it doesn't all disappear into the block, that is not a concern.

Chances are threads on yours will be rolled BTW, high volume production of standard fasteners is virtually all rolled threads these days.

I'm tempted to say fire it up and run it.
But keep a close eye out for any symptoms of head gasket failure.
However it has to be your choice.
It is your risk.
 

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Discussion Starter #7
Thank you both for the responses. I'm sorry for the late response, been busy with work and my grandmother has been sick, she is better now thank god. I managed to buy the original bolts(new) and I was going to tighten them but my dad wanted to make sure the valves all sealed correctly and so we tested that out and it turns out 9 of the valves were not sealing correctly so we spent yesterday and today making sure they sealed correctly. We're almost done with that (just 2 giving us some problems). Tomorrow we're going to tighten them early in the morning before I head off to work and get back to you on how it went. If all goes correctly, we're going to keep going with the assembly and hope everything works fine. I've read on some pages about the crankshaft bolt(I'm traducing the technical terms from Spanish, I'm not sure about the correct translation, I'm sorry). The torque needed on the crankshaft bolt is 110pound-ft?

Also one additional question, we tried to untighten the bolts on the camshaft but they are very very tight and I'm afraid that I'll break them if I keep going. What do you guys recommend I do?

Thank you all very much for your kind answers and I will keep you posted whenever I can on how this adventure is going hahaha.

Enrique
 

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Glad Grandma is feeling better.
Give her a hug, it always helps. :d

Which bolts on camshaft Enrique ????

I would have thought that if you had got to point of getting the head off that you had undone all on the camshafts that is needed ?
 

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Discussion Starter #9
Thank you Dancingdad, already gave her loads hahaha.

There are 2 camshafts correct? I think camshaft is the correct word (ejes de levas in spanish) they both have a bolt that secures the camshaft gear in position, and that bolt is very very tight, I'm not sure how I should go about it to untighten it or if I should just leave it be.
 

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Thank you Dancingdad, already gave her loads hahaha.

There are 2 camshafts correct? I think camshaft is the correct word (ejes de levas in spanish) they both have a bolt that secures the camshaft gear in position, and that bolt is very very tight, I'm not sure how I should go about it to untighten it or if I should just leave it be.
We need to be clear before we answer your question on camshaft/s in your first post you say 1.6v for engine size..is that 16v or 1.6 the 1.6 engine has two cam shafts but the 1.2 16v has only one..
 

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We have a saying.
If it isn't broke, don't fix it.

If those bolts do not need to come out, leave them alone.
As with the head bolts, good chance they are stretch bolts
Some cars the gear needs to come off to get cams in and out.
Others they do not.
 

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Discussion Starter #12
Thank you for your responses.

To phil48: Pardon me, it is Renault Clio 16v 1.6

To Dancingdad :That is a great saying hahaha. My car has 2 cams, and each one with a gear, but in the center of the gear there is a bolt that is very tight, I've read that it has a seal(not sure of the exact translation again) that should be changed. But the bolts are so tight that I'm afraid I'll break something before I manage to get the bolt off, not sure if I should change the seal.
 

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Discussion Starter #16
I am sorry for the very delayed response. My grandmother passed away.We managed to get the car up and running maybe a day before it happened. The car works perfectly, just as it did before, thank you all so much for your help and the information you provided us. I will of course let you all know of any upcoming projects. But for now, it's time to be with family.

Thank you all,

Enrique
 
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