VALVE STEM OIL SEALING ON METEOR MkIVB, M120 or METEORITE

[attleej]

Dear All,

 

The REME Museum's Conqueror ARV has the Meteor M120 petrol engine. Unfortunately it is very easy to wet the plugs with oil. Fortunately it is easy to detect which ones are affected because when they are dry the resistance at the plug lead is infinite but when wet merely 'high'. The Megga easily detects duff ones.

 

I am fairly confident that the oil is getting past the valves because:

 

The compression are satisfactory and most importantly, even.

 

 

 

 

 

The engine was rebuilt at (I think) Aldershot Command Workshops in the eighties. It seems unlikely that they would have assembled it with seriously worn valve guides or valve stems. One would guess that the valves were the same as a Mk IVB so they should have been able to acquire new ones if nec.

 

In the valve gear cross section drawings I can see that there is a 'shield' but I have not yet seen one! Is it made of steel or is it rubber or some other material which can go hard?

[attleej]

Sorry, accidently pressed SEND.

 

Dear All,

 

The REME Museum's Conqueror ARV has the Meteor M120 petrol engine. Unfortunately it is very easy to wet the plugs with oil. Fortunately it is easy to detect which ones are affected because when they are dry the resistance at the plug lead is infinite but when wet merely 'high'. The Megga easily detects duff ones.

 

I am fairly confident that the oil is getting past the valves because:

 

The compression are satisfactory and most importantly, even.

There is no exhaust smoke when engine is pulling, it is clear.

When the engine is 'revved' and throttle released there is always a big puff of blue smoke.

The problem is worst if the engine is allowed to idle too long when cold or revved up and down (as we all love to do!)

 

 

The engine was rebuilt at (I think) Aldershot Command Workshops in the eighties. It seems unlikely that they would have assembled it with seriously worn valve guides or valve stems. One would guess that the valves were the same as a Mk IVB so they should have been able to acquire new ones if nec.

 

In the valve gear cross section drawings I can see that there is a 'shield' but I have not yet seen one! Is it made of steel or is it rubber or some other material which can go hard?

 

Does anyone have any other ideas?

 

John

[w896andy]

John

 

This may or may not be of any use to you as it’s a totally different application. I recently had the cylinder head off of my GMC and found that they have steel shields (or should have) over the top of the inlet valve springs. As a mechanic of the old school I’ve never seen these before but they appear to stop oil being flung over onto the inlet valve and then drawn down the valve stem. I’ve only ever seen valve stem oil seals on OHV engines or nothing at all usually on side valve engines as the oil doesn’t get drawn up.

 

My GMC was a French rebuild that was then stored and never used, it passed through a couple of people before I registered it and put it back on the road so it hadn’t done any mileage or as far as I can see been messed about with since its French army rebuild. It was missing one oil shield with another damaged and a valve guide was worn which I easily sorted. Whilst it didn’t foul plugs it did smoke a little much as you have described so the base rebuild was not perfect, but maybe the French quality control is not as good as the British !!!!!

 

I have attached a picture which shows the shields on the inlets only, in this case they fitted over the valve spring collars and if I didn’t have the head off I could have fitted them in situ. As I say it maybe totally different on a Meteor so this may or may not help you.

 

[Caddy]

Speak to Jersey Aviation. M120 uses a lot of the same parts as the Mk IV Meteor.

When I sorted out a gasket set for a Meteor I ended up getting Merlin gaskets.

The valves, stems, etc should be the same.

[Sean N]

John, at what point when the engine is revved and then throttle released do you get the puff of oil?

 

A Cent parts list I have here covering Meteor MkIV lists shield for the exhaust valve and seal for the inlet, and specifically says the seal is rubber. As you suggest, perished rubber inlet seals would be consistent with your issues. The part number is 3/RR EM5114.

[attleej]

Sean and All,

 

I get the big puff of smoke when the throttle is released. When running at fast idle or pulling there is nothing.

 

What I also forgot to mention was the engine oil got contaminated with petrol from the old mechanical fuel injection pump. That could well have hastened the demise of the seals.

 

John

[Sean N]

I normally find you get the puff of smoke on coming back on the throttle after lifting off, but I know little about Meteors and either way it certainly does sound like valve stem sealing given the symptoms. I refer the honourable gentleman to my previous answer re. seals! Are you contemplating taking it apart, or living with it?

[attleej]

Sean,

I would agree with that. Closing the throttle creates large inlet manifold depression which sucks in the oil. Very little fuel is being burnt, not much heat. I suspect that you are right and the puff actually occurs when you open the throttle a little.

 

I am working up a plan of action for the Conqueror. There are a few issues, namely:

 

The track is too slack because the adjusters are seized solid. (and every tankie who sees it running around will know that the track is too slack but not the reason why)

 

At least one final drive weeps oil.

 

The winch's J60 with auto gear-box only just pulls the full load but the winch will run back when the throttle is released. It needs a 3 :1 step down gear-box with a sprag brake and without it, it will not pass a winch test.

 

The pump for the spades hydraulic system needs to be in the winch compartment where it is more accessible. Then hydraulic barrel needs to be run down to the spade valve block in the transmission compartment.

 

Unbelievably the modern bio-petrol is attacking the soft soldered joints in the fuel system. The system will have to be rebuilt using aluminium.

 

It is very difficult to get the fuel mapping right with a variable load. The plug oiling problem has not helped. I would like to run the engine against a dynamometer of some sort.

 

 

 

This all suggests that the engine needs to come out to do the job properly with good engineering hygene.

 

 

I will finish writing up the plan and put it to the Director of the REME Museum for approval.

 

John