My KV6 Cambelt change

[kaiser]

Originally Posted by Mike Noc

The reason for using the tools is to get the timing spot on.

The tools lock the camshafts not the cam sprockets, so once they are in place you can loosen the sprockets and turn them slightly to get the belt on, and you won't affect the timing.

Is that your problem or have I misread it?

The rear sprockets are keyed, so of course the tools will lock them as they lock the cams.

[Mike Noc]

Yes of course - I should have made it clear I was talking about the front belt and front sprockets as was the OP initially.

Or is the 'problem' that with everything timed correctly the marks on the rear sprockets aren't in perfect alignment?

If so then I'd say forget about the timing marks and go with the tools and the engine will be correctly timed.

[kaiser]

I have re-read the OP about locking the front sprockets.
I understand the problem as this:

You have timed the engine, to your satisfaction and done all the adjustments and released the tensioner, but in order to tighten the front sprockets to the required torque, you have to take safe pin out to be able to move the belt in order to fix the restraining tool.

You can of course do that, provided the front sprockets are tight enough to not move on shafts while you move the belt.

The front belt has nothing to do with the timing at all, except to keep the cams and the crank synchronised. So in essence, very short and to the point. The mark on the crank, must correspond to marks on the rear sprockets. The front belt is just like a bi-cycle chain, it provides the motion.

So you can tighten those nuts in any position of the front belt, provided no sprocket moves, while moving or tightening.

I hope this is what you are looking for?

[p2roverman]

Originally Posted by kaiser

I have re-read the OP about locking the front sprockets.
I understand the problem as this:

You have timed the engine, to your satisfaction and done all the adjustments and released the tensioner, but in order to tighten the front sprockets to the required torque, you have to take safe pin out to be able to move the belt in order to fix the restraining tool.

You can of course do that, provided the front sprockets are tight enough to not move on shafts while you move the belt.

The front belt has nothing to do with the timing at all, except to keep the cams and the crank synchronised. So in essence, very short and to the point. The mark on the crank, must correspond to marks on the rear sprockets. The front belt is just like a bi-cycle chain, it provides the motion.

So you can tighten those nuts in any position of the front belt, provided no sprocket moves, while moving or tightening.

I hope this is what you are looking for?

I was in complete agreement and was planning to complete the job this way. Method being -

1 - Crankshaft locked in the safe position and the marks on the rear chainwheels inline. (Front chainwheels previously loosened and moved enough to get the belt on, then tightened just enough to grip the camshaft)
2 - Remove locking pin and rotate engine enough to engage front chainwheel locking tool, then fully tighten camshaft end bolt

So, firstly, are we are all in aggreemant that the correct camshaft timing is when the rear chainwheel marks align and the engine in safe position (as -1- above)

If so, then we have to allow the front chainwheel to 'freewheel' in order to get the belt on, which, as I have found, will move the wheel so that the locking tool will not engage.

As the whole engine then has to be turned slightly before the tool will engage so that the camshaft end bolts can be fully tightened, then why are there different tools provided for 2 and 2.5 litre engines?

The whole issue seems to resolve over whether aligning the rear chainwheel markings when the engine is in safe position is the true position for correct valve timing for both sizes of engines. If it is, then the issue of tippexing! the front chainwheels is not important as the two camshafts (each head) can both be rotated independently back to that position and locked in position when the rear wheels and belt are fitted.

I think this is key. We need to know the position of the rear chaiwheels (and therefore camshafts) when the engine is in the safe position, and use the tools as assembly aids, rather than timing alignment jigs.

Perhaps I'm making a meal of this, but I feel that correct valve timing is critical to get the best out of these engines.

[Mike Noc]

Originally Posted by p2roverman

So, firstly, are we are all in aggreemant that the correct camshaft timing is when the rear chainwheel marks align and the engine in safe position (as -1- above).

No we aren't - well I'm not anyway. As I see it these particular engines are correctly and accurately timed using the tools - not by aligning the rear cam sprocket marks.

If you know where to look it tells you this in the official RAVE technical documentation.

The chap who designed the tools gave a credible explanation as to why this is the case.

[jn12]

Originally Posted by Mike Noc

No we aren't - well I'm not anyway. As I see it these particular engines are correctly and accurately timed using the tools - not by aligning the rear cam sprocket marks.

If you know where to look it tells you this in the official RAVE technical documentation.

The chap who designed the tools gave a credible explanation as to why this is the case.

Correct Mike.

The tools do perform the task of holding the cams/gears in place in order to undo the sprockets bolts so they can free wheel easing fitment of the belt and tensioning.

They also set the cams at the correct timing for each V6 variant. This results in the rear gears not quite meeting depending on what setting is being used. There are tools and adapter plates for the -

2.0 V6 150
2.5 160/177
MG 2.5 180/190 (The settings are different and handed for the LH and RH hand banks on this variant with the rear bank timing being slightly retarded I think - See RAVE)

Once the front belt is fitted, tensioned, pin pulled, sprocket bolts tightened back up and the front tools removed simply remove the crank locking pin and move the crank pulley back or forth to allow the rear tools to slot in nicely in order to undo those bolts and replace the rear belts etc. Don't do anything to the rears whilst you a busy with the front.

I use this procedure as I have the tools and took on board what the designer intended timing wise as well as the advice given by many rover trained mechanics.

It is of course the most needlessly complicated carry on ever and you do not have to follow it. You can of course replace how you would any other belt and it will run ok with the marks lining up on the rear gears. It was also designed for this in case the tools were not available abroad. However in doing so it will not be quite spot on but I doubt many would notice the difference.

Either way it will work one way or another. If you have the tools to hand you might as well use them as it does make the job easier and I suppose a failsafe when it comes to undoing and tightening the sprocket bolts. There used to be many a story on the old MGR forum of cam ends snapping off.....

[jn12]

Originally Posted by p2roverman

I was in complete agreement and was planning to complete the job this way. Method being -

1 - Crankshaft locked in the safe position and the marks on the rear chainwheels inline. (Front chainwheels previously loosened and moved enough to get the belt on, then tightened just enough to grip the camshaft)
2 - Remove locking pin and rotate engine enough to engage front chainwheel locking tool, then fully tighten camshaft end bolt

So, firstly, are we are all in aggreemant that the correct camshaft timing is when the rear chainwheel marks align and the engine in safe position (as -1- above)

If so, then we have to allow the front chainwheel to 'freewheel' in order to get the belt on, which, as I have found, will move the wheel so that the locking tool will not engage.

As the whole engine then has to be turned slightly before the tool will engage so that the camshaft end bolts can be fully tightened, then why are there different tools provided for 2 and 2.5 litre engines?

The whole issue seems to resolve over whether aligning the rear chainwheel markings when the engine is in safe position is the true position for correct valve timing for both sizes of engines. If it is, then the issue of tippexing! the front chainwheels is not important as the two camshafts (each head) can both be rotated independently back to that position and locked in position when the rear wheels and belt are fitted.

I think this is key. We need to know the position of the rear chaiwheels (and therefore camshafts) when the engine is in the safe position, and use the tools as assembly aids, rather than timing alignment jigs.

Perhaps I'm making a meal of this, but I feel that correct valve timing is critical to get the best out of these engines.

Locking the crank with the pin properly in place and crank sprocket lined up to it's mark the rear cam shaft gears will not meet exactly. Use the front tools and fit new belt then once done removed the tools then start on the rears.

[beinet1]

Hi,

I guess this discussion will go on forever.
Just for information, I have copied and pasted some information below which I am in the belief was written by one engineer involved in the design of the KV6 engine, which might be of interest:

I don't want to argue the point with you yet again so will not be making further posts in this thread, but as the designer of both the cam drive system and the setting tools, I think I have some knowledge of why the tools should be used whenever possible.

Just for information, I did issue an instruction for setting the timing without tools for use on Diplomatic Service cars. This was achieved by scribing new timing marks on the rear pulleys rather than using the existing marks. These are only there to aid positioning and to set timing between the inlet and exhaust cam. It is only coincidence that they nearly align when the engine is set to its timing position. Perhaps I should have moved the marks round a few degrees to avoid the confusion.

If I remember correctly, the fixed marks on the rear pulleys give balanced timing between the inlet and exhaust profiles. On many engines this turns out to be the optimum setting and is a good place to start. However, production tooling is frozen at least 12 months before job 1 whereas the engine tune including ignition, fuel and cam timing are subject to change right up to the wire and sometimes well beyond. The optimised setting for cam timing on the V6 turned out not to be the balanced setting, but was a little retarded (or was it advanced?) from this position and this timing figure is set by the front timing tool. It changed again for the 190 engine and this requires another setting.

The marks on the rear pulleys are still required in order to set the timing between inlet and exhaust cams. This was originally going to be a floating setting as used on the front, but it was found that we could get away with fixed pulleys (just!).

That really is about all I have to say.

Correct use of the tools also prevents damage to the camshafts while tightening the bolts as you mention.

The engine has "floating" front pulleys (not positively keyed to the cams) because there is so much tolerance build up in the cam drive system. The cams are therefore positioned by the setting tools and then the pulleys bolted up tight. Because this system was being used, the length tolerance of the belt was left very wide. If the pulleys are left in position, the new belt may well be of significantly different length to the old one. This will affect the cam timing.

In practice, you would be very unlucky to have the original belt at one end of the length tolerance and the replacement at the other so the engine will probably run OK.

The rear belts are a bit tricky with no fitting tools, but it can be done.

I would change the pump and tensioner at the same time.

You will not be able to measure the difference between the belts, just go for it and hope. Mark up the old belt against marks on the pulleys, then transfer these marks to the new belt.

You can remove the bolts for the rear belt pulleys. In fact, you will have to, but they are keyed so will go back on correctly. The problem is that the tooling puts tension on the belt before it is fitted. You could probably get round this using a wooden wedge between the pulleys or something?

Something to remember when doing up the pulley bolts - hold the camshaft at the same end as the bolt you are working on. The cam itself is not designed to react this sort of torque down its length.

And if you look at the Landrover official RAVE publication for replacing the KV6 timing belts you will find this;

Refit:
NOTE: Following front or rear timing belt
refitment, it is possible that, after rotating the
engine and positioning the crankshaft pulley to
the 'SAFE' position, the timing marks on the
rear timing gears may be misaligned. This
misalignment is acceptable provided that the
timing belt refitting procedure was carried out
correctly.

[p2roverman]

Thanks to Beinet for your post which confirms that the marks on the rear chainwheels do NOT quite align when the engine is in 'safe' mode.

I'll hopefully get the primary belt on today before posting again.

[kaiser]

That explanation is complete gobbledygook And I don't care who or what this person claims to be or have done!

And to claim that the rear and the front bank should have different timing is a sign of not understanding an iota of what is going on. This is about the dumbest I have heard in this discussion, to be quite honest. Who in their wildest dreams would give the first 3 cylinders one timing and a different timing for the last three cylinders on a straight 6?? Who? Blinking nonsense!

Of course the rear marks can be made to align perfectly! And if that is the correct setting (which I seriously believe it is), could have been found out this time, as the OP had a factory set engine, and could have verified this with a photograph.
It still can be found out, if you believe the special tools, because if the tools are fitted, where are the marks?
Take a photo and let us see!

That Diesel 1956 comes with a statement of pre-production delays is absolute nonsense. Once the correct timing is established for the engine, it is possible to make correct marks very easily, for Pete's sake, we are talking about two dimples, or marks, that is all. You don't need 12 months to make that. You can scribe this unto the sprockets when you assemble, if need be.


I think we are discussing with a bunch of people many of whom really do not understand how an engine works.

And for people that quote and paste or refer to information, give a link so people can go and read the whole story, don't just quote selectively.