Cambelt / Timing belt change guide

[Fred@BTM]

i've been through this about a million times but here goes!

lets start with an engine that is timed up perfectly from factory, when i say perfectly you can only use maximum of 3 finger from 1 hand to fit the horseshoe - anymore than that the the timing IS NOT right

now you replace the cambelt WITHOUT undoing the inlet/exhaust pullies, like a lot of engines (we shall call it THE TIPPEX WAY)

replace the belt, tension it up - surprise, the timing tool doesn't fit

WHY???

because when you fit a new belt and tension it you are tensioning the belt between the exhaust pulley and the crank ONLY, the rest of the belt run won't be 100% tight, you spin it over, the belt tension equalises - hey presto the timing is out


Hence why you change the belt using the correct method of undoing the pullies, fitting the belt, spinning the whole lot backwards to equalise the belt tension, then tighten it all up


I'll do a video sometime showing what happens

 

[Chip-mk1]

Exactly Fred, and thats why when local garages do it the timing is normally slightly out, exaggerated by the fact that over time the belts very slightly stretch so each time you do it with a new belt instead, youve moved it slightly as you keep putting an unstretched belt on the stretched timing and then when it stretches it gets a tiny bit worse.


It will then run fine, drive ok. seem alright, so the garage think they have done it properly except for later on the owner discovers a bit of missing torque and that it is not quite as good on fuel, and then people post on here asking why there car isnt as quick as their mates one etc.

 

[sam JFM]

So how do you know when you have the belt tension right? because after you he turned the engine over with the pulleys loose the tensioner is still on its marks and does not fluctuate when turning it over with everything undone?

 

[Chip-mk1]

It will move about a bit as you turn it over, but should broadly line up

 

[sam JFM]

And then with everything tight when you turn it over the tensioner should move as it takes up the tension in the valve train but return to its marks when at TDC again correct?

 

[mark123]

i've been through this about a million times but here goes!

lets start with an engine that is timed up perfectly from factory, when i say perfectly you can only use maximum of 3 finger from 1 hand to fit the horseshoe - anymore than that the the timing IS NOT right

now you replace the cambelt WITHOUT undoing the inlet/exhaust pullies, like a lot of engines (we shall call it THE TIPPEX WAY)

replace the belt, tension it up - surprise, the timing tool doesn't fit

WHY???

because when you fit a new belt and tension it you are tensioning the belt between the exhaust pulley and the crank ONLY, the rest of the belt run won't be 100% tight, you spin it over, the belt tension equalises - hey presto the timing is out


Hence why you change the belt using the correct method of undoing the pullies, fitting the belt, spinning the whole lot backwards to equalise the belt tension, then tighten it all up


I'll do a video sometime showing what happens

But if the timing is out after turning it over you adjust it and retension. This time the tension is spread throughout the belt and the timing and tension stay correct.

My pdf clearly shows the dephaser present for the procedure without undoing the cam pulleys.

 

[Fred@BTM]

But if the timing is out after turning it over you adjust it and retension..

but then you should've just done it the way i describe in the first place? As you now have to get the pulley tool out, and slacken off the inlet/exhaust and crank!

 

[Chip-mk1]

But if the timing is out after turning it over you adjust it and retension.

How without the tools?

 

[mark123]

but then you should've just done it the way i describe in the first place? As you now have to get the pulley tool out, and slacken off the inlet/exhaust and crank!

No you just undo the crank pulley as per procedure 2.

You haven't explained why VVT would make a difference between the two procedures. I might make a video myself lol.

How without the tools?

With the horse shoe and crank pin. As above.

 

[Fred@BTM]

Won't work!

 

[Chip-mk1]

No you just undo the crank pulley as per procedure 2.

You haven't explained why VVT would make a difference between the two procedures. I might make a video myself lol.



With the horse shoe and crank pin. As above.

How though?

How will you tighten the crankpulley?

Cause you can only move it whole teeth if you havent loosened the pulleys, so you need to loosen them, and then when it comes to tightening them you can damage the cams if you rely on the horseshoe to hold them in place, and more to the point you CANT time it accurately like that as you will have the cam locked out against the tool, so its never going to be set so the tool can easily slide in and out.

You have to be able to lock the pulleys to accurately time it, otherwise the best you will achieve is within a few degrees, and thats enough to negatively impact performance.

 

[mark123]

It does work thought Fred. I've done it.

If the timing is correct when you start there is no reason why you cannot get it correct again just undoing the crank pulley.

If you think about it, not undoing the cam pulleys is just like if they were held in place by a woodruff key. That works for the vast majority of cars so why wouldn't it on the F4R.

I don't expect I will ever convince you. I just can't see anything wrong with my logic, if you can please point it out. If I ever get the time I'll do a video

 

[Chip-mk1]

It does work thought Fred. I've done it.

If the timing is correct when you start there is no reason why you cannot get it correct again just undoing the crank pulley.

If you think about it, not undoing the cam pulleys is just like if they were held in place by a woodruff key. That works for the vast majority of cars so why wouldn't it on the F4R.

I don't expect I will ever convince you. I just can't see anything wrong with my logic, if you can please point it out. If I ever get the time I'll do a video

And what if the timing wasnt perfect in the first place?
The best you can ever hope to achieve is make it the same as before, you cant ever correct it.

 

[Addicted]

It does work thought Fred. I've done it.

If the timing is correct when you start there is no reason why you cannot get it correct again just undoing the crank pulley.

If you think about it, not undoing the cam pulleys is just like if they were held in place by a woodruff key. That works for the vast majority of cars so why wouldn't it on the F4R.

I don't expect I will ever convince you. I just can't see anything wrong with my logic, if you can please point it out. If I ever get the time I'll do a video

There's the fault in your logic, you assume it's correct rather than doing a proper job in the first place and ensuring its correct

edit: Seems I was slow to the mark!

 

[mark123]

And what if the timing wasnt perfect in the first place?
The best you can ever hope to achieve is make it the same as before, you cant ever correct it.

But that is a separate matter - you would need to undo all the pulleys in that case.

My point has always been that there is no reason you cannot get the timing correct again without undoing the cam pulleys, as long as you started with it correct for the old belt.

 

[mark123]

There's the fault in your logic, you assume it's correct rather than doing a proper job in the first place and ensuring its correct

edit: Seems I was slow to the mark!

lol. It is still a proper job. If you start with a car that has been timed incorrectly you have to do extra work to remedy that.

You're drifting off topic. The debate was about whether procedure 2 in the pdf (not undoing the cam pulleys) can get you the correct timing. I've always maintained that it can Fred says it won't work.

 

[Addicted]

lol. It is still a proper job. If you start with a car that has been timed incorrectly you have to do extra work to remedy that.

You're drifting off topic. The debate was about whether procedure 2 in the pdf (not undoing the cam pulleys) can get you the correct timing. I've always maintained that it can Fred says it won't work.

But that's the point, you can't tell 100% if it has been timed correctly, so surely it's better to just do it the right way in the first place to avoid timing it back up to an incorrect timing?

Back to the point, you don't know if it's correct timing as you aren't checking if it is, you are just putting it back to what it was previously, which may or may not be correct

 

[Chip-mk1]

But that is a separate matter - you would need to undo all the pulleys in that case.

Indeed, and that case is most of the time.
Also dont forget the belts stretch over time too which alters the timing slightly.

My point has always been that there is no reason you cannot get the timing correct again without undoing the cam pulleys, as long as you started with it correct for the old belt.

If it was correct on the stretched old belt, it wont be on the unstretched new belt.


And the thing that you seem to be missing, is that even from the factory, they seem to vary a lot in the accuracy of the cam timing in the first place, so what chance if you just hope to try and keep it as it was do you ever have of maximising the performance of your car, most people with these cars dont just want the performance (and hence cam timing) "ok" they want it as good as possible.

 

[p@blo]

But that's the point, you can't tell 100% if it has been timed correctly, so surely it's better to just do it the right way in the first place to avoid timing it back up to an incorrect timing?

Back to the point, you don't know if it's correct timing as you aren't checking if it is, you are just putting it back to what it was previously, which may or may not be correct

Didn't realise you'd changed the belt on yours.

 

[Addicted]

Didn't realise you'd changed the belt on yours.

I never said I had, I have been reading and understanding whats going on, you know, learning?

If I'm wrong feel free to correct me, but not sure what that has to do with anything.

 

[p@blo]

I never said I had, I have been reading and understanding whats going on, you know, learning?

If I'm wrong feel free to correct me,but not sure what that has to do with anything.

From the way you were talking, It did seem to be very much implied. Appreciate you clarifying.

In all seriousness, weren't you recently flummoxed by a noise in or around the exhaust (area)? Would you actually have a clue what you were doing?

:quiet:

 

[Chip-mk1]

But that's the point, you can't tell 100% if it has been timed correctly

Yes you can, very easily, all you need to do that is the crank pin and the horseshoe, its adjusting it that requires the pulleys to be locked, not just checking it.

 

[Fred@BTM]

Well i've gone and bought a 182 this morning so i'll prove my point in the next few weeks!

This is the problem we (all the specialists) have Mark, 1 mechanic does a belt change on an F4R once and thinks its right, it isn't (not having a dig BTW)

if the procedure you're on about is correct why do we see so many done wrong? I've had TWO come in with correct timing this year out of about 170, so either 168 or so were right and i'm wrong or only 2 were right, what are the odds?

 

[Addicted]

I'll get back in my box

 

[p@blo]

I'll get back in my box

Likewise, I'm going back under my bridge :rasp:

<hug>

 

[mark123]

But that's the point, you can't tell 100% if it has been timed correctly, so surely it's better to just do it the right way in the first place to avoid timing it back up to an incorrect timing?

Back to the point, you don't know if it's correct timing as you aren't checking if it is, you are just putting it back to what it was previously, which may or may not be correct

Part of the procedure is fitting the tools before you remove the old belt. At that point it is obvious whether the timing is out or not before you start. So you can tell.
Chip-mk1 how much do belts really stretch in practice? If it was to any significant degree surely the timing would be out on all cars that didn't have floating pulleys?

Well i've gone and bought a 182 this morning so i'll prove my point in the next few weeks!

This is the problem we (all the specialists) have Mark, 1 mechanic does a belt change on an F4R once and thinks its right, it isn't (not having a dig BTW)

if the procedure you're on about is correct why do we see so many done wrong? I've had TWO come in with correct timing this year out of about 170, so either 168 or so were right and i'm wrong or only 2 were right, what are the odds?

Maybe they don't even follow that procedure correctly? They are out from the factory like Chip says?

 

[Fred@BTM]

no idea how they do them at factory, but i now the guy who does/did look after all the R-sport race engines for the clio cup and formula renaults, he uses the pulley tool

 

[Chip-mk1]

Part of the procedure is fitting the tools before you remove the old belt. At that point it is obvious whether the timing is out or not before you start. So you can tell.
@Chip-mk1 how much do belts really stretch in practice? If it was to any significant degree surely the timing would be out on all cars that didn't have floating pulleys?

TBH I think that the belts possibly vary slightly when new, which is more of a concern.

If they were all totally identical when new, and they stretched over time then what would happen (assuming timed correctly) using your method is:
New belt timed correctly
Stretches slightly so timing goes out a tiny bit over time
New belt fitted on same timing, timed correctly again

But I think there is more to it than stretch, I think there is a production tolerance on the belts personally.

Maybe they don't even follow that procedure correctly? They are out from the factory like Chip says?

Plenty seemed to be wrong when they had their first ever belt change, so either they were out to start with or they stretched.

 

[Fred@BTM]

i very much doubt the belts stretch as much as you make out, i've used them to lift engines etc, they're bloody strong!!

tolerance is a different matter, the new modified kits don't seem to need tensioning up as much as the old ones (another reason why the pulley tool is needed )

 

[Chip-mk1]

i very much doubt the belts stretch as much as you make out, i've used them to lift engines etc, they're bloody strong!!

I havent made out they stretch a lot, just said it may be a small factor, but degradation over time is very different to if they are strong enough to lift an engine for a few seconds or not.


Like I said in the post above yours, I think its more about production tolerance on the belts.

tolerance is a different matter, the new modified kits don't seem to need tensioning up as much as the old ones (another reason why the pulley tool is needed )

Agreed, Mark123's method relies on the belt being the same overall length, if there is a tiny difference in length though for the number of teeth gap between the top pulleys and bottom one, the timing will be out.

 

[mark123]

no idea how they do them at factory, but i now the guy who does/did look after all the R-sport race engines for the clio cup and formula renaults, he uses the pulley tool

So do I on my race car I just don't bother on the road car if I want to cut the time down a bit.

I'm not disputing that using the pulley tool is the best way.

 

[Chip-mk1]

So do I on my race car I just don't bother on the road car if I want to cut the time down a bit.

I'm not disputing that using the pulley tool is the best way.

FLOL!

Kind of shot your own argument in the foot there mate.

 

[mark123]

I know lol.

 

[VikkiB]

if the procedure you're on about is correct why do we see so many done wrong? I've had TWO come in with correct timing this year out of about 170, so either 168 or so were right and i'm wrong or only 2 were right, what are the odds?

At the moment, Dan seems to be seeing more and more with the crank timing out.

 

[Tilenkris]

Well i've gone and bought a 182 this morning so i'll prove my point in the next few weeks!

This is the problem we (all the specialists) have Mark, 1 mechanic does a belt change on an F4R once and thinks its right, it isn't (not having a dig BTW)

if the procedure you're on about is correct why do we see so many done wrong? I've had TWO come in with correct timing this year out of about 170, so either 168 or so were right and i'm wrong or only 2 were right, what are the odds?

Jesus tap dancing christ, now I'm getting worried about mine...

 

[MG cup]

Lol this old argument.

Marks theory is right if its good to start with. As he says its absolutely no different to a set of woodruff keyed pulleys which are obviously timed right from factory on other engines, in fact its easier to do on a Clio than other cars by only slackening the crank as it has a floating pulley which most engines don't.

You will know if you have done a lot of different belts that you have to strategically place cams and cranks away from the timing marks in the procedure as when you tension the belt it always pulls the pulleys round to line up with them.

 

[Chip-mk1]

Lol this old argument.

Marks theory is wrong if like the vast majroity of clios its not correct to start with.

As it is different to a set of woodruff keyed pulleys which are obviously timed right from factory on other engines where as on the clio they could be absolutely anywhere depending on if youve ovrerevved it to make them slip slightly or if the previous monkey did it wrong.

In fact its easier to inherit a wrong setup on a Clio than other cars as it has a floating pulleys which most engines don't.

EFA

 

[MG cup]

Lol.

If you set up an engine tonight correctly with all genuine tools you could replace the belt tomorrow with just the crank pin and horseshoe so his theory is right.

 

[Chip-mk1]

Lol.

If you set up an engine tonight correctly with all genuine tools you could replace the belt tomorrow with just the crank pin and horseshoe so his theory is right.

Except the new belt might be slightly different length to the last (which is a risk on other engines too and part of the reason that manufacturers move to unkeyed designs so they can correct for it easily)

(or did you think it was just to save 2 quid on a woodruff key? lol)

 

[MG cup]

Except the new belt might be slightly different length to the last (which is a risk on other engines too and part of the reason that manufacturers move to unkeyed designs so they can correct for it easily)

(or did you think it was just to save 2 quid on a woodruff key? lol)

No different to what could happen between any other engine or belt manufacturer with all pulleys keyed.

Try doing a belt on a quad cam v6 with no locking pins or dialing in a rotary fuel pump for 1mm lift on the cam with 3 degrees before TDC with no locking tools and a Clio belt is a pisser.