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MG MGF Technical - VVC engine

Hi guys
advice please. I had tappety noise on my TF 160. When the engine was stripped down today they found that all the tappets and one cam had been damaged. The garage said that the Cam had caused the tappets to fail. Does this sound correct?

The car has never been short of oil and has been serviced according to schedules.

Also the bill has doubled from £960 to £2000 so is this the going rate at an MG Dealers.
Martin Smith

This is a rare occurance for the cams and tappets to fail. Do you have pictures??Do you know what has caused the failure, oil starvation?? Could be oil pump if that is the case. If it is the cams and tappets then this is not such a big job as the work can be done by removing the cam carrier and replacing faulty parts, about 4 hours work.
mike

I can't see how a cam can damage a set of tappets Martin.

What is the vintage of your VVC? At some time during the last year of production, MG Rover changed suppliers from the Chinese company - would be interesting to know whether yours is one of these later cars.
Rob Bell

With respect.. I have seen a large number of VVC heads and can say categorically that the inlet cams have a tendecny to cause heavy pitting on the surface of the followers due to metallurgical differences and the width/offset of the lobes not turning the followers correctly. In my experience, a linishing of the followers isusually all that is required to correct the problem, which will re-appear in 10-15,000 miles. It rarely affect the running of the engine and jist gives a little noise.

£2000 is barking mad, You can effect that repair for around £400 even with *new* followers.

Dave
Dave Andrews

Thanks for that info Dave - I was unaware of this problem. How does it manifest? Increase noise? Or is it something that is found incidently while the engine is apart for some other reason?
Rob Bell

"I can't see how a cam can damage a set of tappets Martin."
The cam material is extremly hard and causes wear to the 'softer' tappet material, also the QC of the tappets is probably not as strict as the cams. I have e.mailed this thread to the manufacturers of the cams to see if they can comment. I would have thought that the machining of the head would be more likely to be a problem with tappet rotation rather than lobe offset design.
let's see if we can get a comment from the manufacturers.
mike

Nice one Mike - it will be very interesting to hear what the OEM say. :o)

Cheers
Rob Bell

Thanks guys for the advice. I will try to take some photos tonight

Martin
martin Smith

We made all VVC units supplied to Rover and over the years I have seen many engines with all types of mileages. Pitted followers were never an issue raised in service or in the several tens of thousands of hours testing that was carried out. Failure of the followers to rotate would cause scoring not pitting. Is the oil being changed by mileage, on low annual usage acid build up in the oil could be the cause. Any chance of of a digital picture of the pitting?
Ken Wright

Hi Ken, thanks for your response. If I have a search round I could find a few tappets that have suffered fretting to the surface, as Dave has commented this can usually be linished outbut may return. This may indicate a fault in the surface treatment of the tappets.Lets see if any pictures are taken.

" At some time during the last year of production, MG Rover changed suppliers from the Chinese company" Rob this is a interesting comment can you elaborate??
mike

I dont think the followers are at fault, it is a fault I have found on *every* head I have examined on one or more followers even at very low (4000) mileages. The problem never occurs on the exhaust followers and the follower bores are essentially identical.

There is definitely a problem and it is confined to the VVC side of things.

Dave
Dave Andrews

>> " At some time during the last year of production, MG Rover changed suppliers from the Chinese company" <<

I didn't exactly type that well - typing too fast! What I've been told (this is information is 3rd hand)is that all the VVC units had been supplied by a single UK supplier (that'd presumably be you Ken, and Airtex?). But MGR saught to reduce the cost of these units within the final 6-12 months of production. Plus, I gather, the UK company was getting fed up with unpaid bills. From what I am told, the supply contract went to a company in China who built the VVC units to the original blue prints.

The interesting part of the story is that the UK supplier had modified the design to make it more reliable - such that the VVC supplied has some detail differences that Powertrain were not aware of, and these differences were not, therefore, passed onto the new supplier.

I have to emphasise that this is 3rd hand information - but it would be useful to know whether it is entirely accurate or not. There may be differences in ownership experience between owners of late TF160s and earlier VVC equipped cars attributable to this change.
Rob Bell

Rob, Ken might be able to comment re the supply of these units AFAIK Airtex have made all the VVC units up to final build and manufacture has now gone to China.. however not all the information is on the drawings as you have indicated and this may be detrimental for future VVC production.
Dave, perhaps because the VVC cam is of a different (higher) material spec to the exhaust cam is the main reason..dunno although I have seen lots of VVC heads that haven't suffered from this problem, maybe Ken can comment he is the man qualified to do so.
mike

We have had two VVC head jobs in this week and both have wear/fretting on the exhaust tappets but not the inlet...I know Ken is decommisioning one of the factory units so may be to busy to comment at the moment.
mike

Look forward to hearing what Ken has to say - this is shaping up to be a very informative thread!
Rob Bell

boy oh boy how rumours do spread.
We were the only supplier of VVC units to Rover. We were still supplying until the day that they went to the wall. The only part of the rumour that has some base is that the drawings do not tell the whole truth and if you think about it, it would be silly to put 5 years development and testing on a drawing for someone to steal.
The VVC cams were sintered and were a completley different material to the exhaust cams. Please can someone out there show me a photo of a pitted follower, I remake the point that the follower would not pit if it was not rotating, it would score or, as I have seen, have a groove worn right across it.
Mike makes the point about future VVC production, anyone brave enough to try to copy the unit will either need a of of time and money or to have head hunted someone who really knows how they were made.
ken wright

Glad they weren't Chinese whispers Ken! ;o) (Sorry, couldn't resist)

Thanks for that information - consider that rumour as being put to bed.

Will be interesting to hear your opinions on the problems perceived by Dave and Mike - hopefully someone can send you some suitable images.
Rob Bell

Whilst on the subject and not wisihing to grind The Axe, I would like to know how many people have suffered VVC cam failure, especially at such a low age and mileage -13 months/14K/3rd oil change.

The VVC cam snapped on cylinder no.4

Lord Sward

I have seen this happen , it might have been your engine?? It is pretty rare AFAIK. The cams are joined at this point by a type of brazing,not sure of the correct process and would be the most likley place to fail. The company that make the camshafts (maganese bronze, google that;-))would be the best to answer this if they received the failed parts back from any Rover warranty claims.
mike

Lord Sward - now where have I heard that name before ;o)

Is this on your TF160???
Rob Bell

Okay, I accept I may have been unlucky for the camshaft to fail, but is there anything I could have done to cause it and/or prevent it from happening again? The Cressmeister is now reluctant to caine it as much and has lost a bit of confidence in it.

Still, the VVC unit feels incredibly strong now its got the ITG back on it. A real flying machine.

Rob, my (award winning)TF is a lowly 135 I'm afraid. Bought for the chassis number.......
Lord Sward

I have a large box full of scuffed followers from the VVC inlet cams, I have taken a photo of the last 8 inlet followers I took out, if someone knows how to post a link to the photos I will FTP them to my webspace.

Dave
Dave Andrews

Dave, just place the URL in your posting and it becomes a live link in the thread (just remember to include the http:// tag)
Rob Bell

Dave e-mail direct to ken his address is above.Mike.
Steve, I would think you would be very unlucky for it to happen twice on the same engine...
mike

Thanks for the vote of confidence Mike!
Lord Sward

See these followers, one is ver bad and untypical, the rest have typiccal damage

http://members.aol.com/DVAndrews/vvcfoll.jpg

Dave
Dave Andrews

Interesting picture Dave - but I don't know how to interpret it. Can you explain what the discolouration means?

Cheers
Rob Bell

I have forwarded the pictures on to Ken Wright for his comments. My first reaction is that it is a lubrication problem. The exhaust cams tend to be better lubricated, due to the angle of the engine the oil collects in the area of the exhaust cam and drains dow off the inlet cam, by nature of the VVC cam material it will be more damaging to the follower if lubrication is lacking. Only my opinion though,FWIW.
mike

Whenever I fit one piece solid cams in replacement of VVC mechs the problems do not recur, that would suggest that lubrication is not lacking or the problem would afflict the new cam and followers.

Dave
Dave Andrews

Dave, I can only suggest that when the solid cams are fitted the lubrication demands are altered due to the VVC units being omitted therefore restoring better oil feed to the followers. I have always maintained that the oil feed to the VVC units need improvement or separate oil feed. That single badly worn follower may be a clue to the start of oil feed problems in that particular case.
mike

This thread was discussed between 25/11/2005 and 17/12/2005

MG MGF Technical index

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