MG ZT 190PS with 180 (177) timing is thus possible

[marinabrian]

Originally Posted by Matt G

Firstly, Thank you all for the really positive and most useful info.

To confirm my locking kit is the sealey set and yes I have the standard 2.5v6 locking plates and the additional mg190 plates too. As the rear cambelt pulleys did not align (by about 2 belt teeth) I decided to check the alignments before slackening the belt.

Basically in the safe position the 180 locking plates fits perfectly and the 190 ones did not suggesting it had been timed in that manner.

Thanks for the engine number info and also heads stamping info, I’ll check that tonight if time after work.

I’ll keep you updated in case this occurs to anyone else, in the future. But basically the plan is too.

1.)Mark up the belt and pulleys in the current timing config, so if I am wrong or make a mistake I have a reference point to go back too.
2.) slacken the belt main belt and align the camshaft with the 190 plates and then I am hoping the rear belts will re align those couple of degrees and restore faith. If not back to the drawing board.

I have heard it is easier to replace the rear belts first using relative belt position rather than notches and re tensioning off the main cambelt exhaust camshaft.

Also thanks for the info about the belt tensioning pulley. I’ll cross check that too when 5 time comes.

Last question am I right in think, that with this engine if miss timed in the wrong timing position (either 180 or 190) there is no chance of damaging the engine I.e the valves hitting the pistons?

Regards

Matt

The timing will be four degrees out timed with 177 tools, but no you won't find the valves hitting the pistons

[chris75]

Matt , if you have the Sealey tools then I assume you also have the Sealey instructions ? Follow the section 4.2 re the rear belts and you won't go wrong
In case you don't have the instructions I have attached them here .
I didn't need to remove the crankshaft locking pin to do mine , and when refitting you rotate the exhaust camshaft as described . Easy

[Mike Noc]

Originally Posted by Matt G

Last question am I right in think, that with this engine if miss timed in the wrong timing position (either 180 or 190) there is no chance of damaging the engine I.e the valves hitting the pistons?

Regards

Matt

Whenever I do timing belts I always slowly go round two revolutions by hand with the spark plugs out, just to ensure nothing touches that shouldn't.

[SD1too]

Originally Posted by Matt G

Basically in the safe position the 180 locking plates fits perfectly and the 190 ones did not ..

Two points on this Matt:

• It’s incorrect to refer to the Rover 177 Ps 2.5 litre KV6 tools as “180 locking plates”. They are not. The MG 180 automatic transmission engine has the same valve timing as the manual 190, so the 190 tooling is used on both.
• As I said, don’t confuse yourself by trying to fit the locking tools to your existing belt set-up. Proceed with removing the old belt and use the 190 tools when fitting the new one. All will be well!

1.)Mark up the belt and pulleys in the current timing config, so if I am wrong or make a mistake I have a reference point to go back too.

Matt, there’s no point in doing this. Since the front inlet sprockets are ‘floating’ any marks you make will only confuse. Secondly, if you have the special tools then marks are unnecessary. Just fit the tools and your engine will be correctly timed, it’s as simple as that!

2.) slacken the belt main belt and align the camshaft with the 190 plates and then I am hoping the rear belts will re align ....

They won’t. As I said, having fitted the front belt do not refit the front tools. You will need to remove the flywheel pin and rotate the engine very slightly to align the rear notches. You must do this otherwise you won’t be able to fit the rear tools and therefore will be unable to undo the rear sprocket bolts safely.

Last question .. if mis-timed in the wrong timing position (either 180 or 190) there is no chance of damaging the engine ...

If you use the flywheel locking pin the engine will be in the safe position. The slight adjustment I’ve mentioned will still be safe. So no, there is no danger of damaging the engine.

Simon

[Mike Noc]

Originally Posted by Matt G

Also the rear cam belts seem to be slightly out as well.

Originally Posted by SD1too

We’ve all found this to be the case. When you’ve done the front belt you will have to remove the flywheel locking pin and move the engine very slightly in order the align the rear sprocket notches. The rear holding tools can then be fitted.

So it would appear that 1955diesel was right all along then Simon.

[Bolin]

Originally Posted by Matt G

Basically in the safe position the 180 locking plates fits perfectly and the 190 ones did not suggesting it had been timed in that manner.

If the belts are original, it is possible that there has been some stretch that has moved the timed position such that it is now closer to the 2.0/2.5/160 position

But as above, just change them as per the book and use the 190 plates and it will be correct.

Originally Posted by Mike Noc

So it would appear that 1955diesel was right all along then Simon.

Mike, 1955diesel was, I believe, referring to the position marks on the earlier 800 version of the KV6 which had floating rear sprockets. I believe that for the later 75/45 KV6 that the rear sprockets should be pretty much aligned when new belts are fitted, irrespective of power output - no not 100% spot on but close enough so that it is technically possible to fit the rear belts with the front tools in place (just about!), which I achieved.

[Mike Noc]

This is what he wrote Colin, and he mentions fixed marks on rear pulleys and the 190 engine:

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.

All academic to me, as I currently don't own a KV6, but I am interested in exactly how these engines were put together.

[Matt G]

Thank you all, for the brilliant technical info.

I have tried to find a 190 stamped on the head, but I cannot seem to find it anywhere.

All being well and work permitting, i’ll try and change the belts in the next couple of days, utilising all your great advice. I’ll keep you posted on how it goes!

Regards

Matt

[Matt G]

Thought I would post a quick update.

After a lot of checking and then double checking, and an odd bit of blasphemy I have managed to change the belts on my mg zt.

I did keep to the plan of marking the belts and sprockets for reference points and it paid off. Although I did use the locking tools for the main job in hand.

My mg Zt had been miss timed to the standard 2.5 v6 settings and also the 14 year old primary timing belt had stretched to the point that the tensioner had just about reached its stop and was letting it slacken off. Having purchased the car like this, it was a good decision not to start or drive it until I had changed the belts, so crisis avoided.

Once aligned with the correct 190 locking tool all my rear camshaft belt marks lined up perfectly. And with my markings, both front camshaft where exactly 1 tooth out (approx 4 degrees) out on both sides.

Also by counting the belt teeth between my markings also help confirm that I was not 1 tooth out either way when I fitted the new belts.

Sd1too thanks for the gen about setting the tensioner pulley, that I certainly would of over looked if you had not of mentioned it.

But anyway thanks to SD1too, Phil-T4, marinabrian, mh007, coups, chris75, bolin and Mike Nocs for brilliant advice, it certainly helped guide me through the job in hand.

Regards

Matt

[SD1too]

Thanks for the report Matt; it's very useful to all of us.

Originally Posted by Matt G

... the 14 year old primary timing belt had stretched to the point that the tensioner had just about reached its stop and was letting it slacken off.

That sounds to me as if, at the previous belt change, whoever did it (garage or DIY owner) did not know that the tensioner pulley has to be set-up very carefully. Who can blame them? I only found out through being a member of this club.

So I don't actually think that your belt had stretched Matt. If it had, to the extent you describe, the enlarged teeth would have popped out of the sprocket slots long ago. Also, if your 14 year old belt had stretched, why hadn't mine which was 19 years old? The difference is that my belt & tensioner hadn't been touched since the car left the factory.

Once aligned with the correct 190 locking tool all my rear camshaft belt marks lined up perfectly.

That's interesting and I suppose makes sense since the relative position of both camshafts has to remain the same on 190 & 177 engines. Thanks for pointing this out.

Sd1too thanks for the gen about setting the tensioner pulley ..

It's a pleasure Matt. I'm convinced that this, and the condition of the associated pulley bearing, are the reasons why a very, very small number of KV6 primary belts come to grief. It's good to know that yours won't be one of them; a job very well done! I hope that it will encourage others.

Simon