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MG Midget and Sprite Technical - Oil collector gauze

Hi,

I’ve been burning a lot of oil recently and getting blue smoke out of the exhaust, so decided to check my breather / vacuum system.

Part of the problem could be a blocked oil filler cap which needs a good clean. Not sure it was letting much air through it. Also checking the pcv valve is operating properly. Although I replaced the rubber gasket I think the tiny internal value might have crud in it causing it not to close fully and so letting oil passed.

When I was rebuilding the engine I did try to flush the gauze in the oil collector with white spirit to help remove all the oil. As it turned out it needs to be replaced as it is gunked right up.

I’ve been advised to buy copper steel wool cleaning scourers as in the photo.

What I wanted to ask was when refitting the new gauze should there be a gap at the top or bottom, or should the gauze completely fill the chamber?

I thought it should sit at the top with a gap at the bottom so oil cannot get sucked up.

Thoughts welcome

Thanks

James






James Paul

Hi James
If you were a member of MASC you might have seen my article a few years back where I advocated the use of stainless steel scouring pads that are readily available from the local store !
Cheers
S G KEIL

Hi S G

Thanks for replying.

Yes I heard scouring pads were great replacements and the copper coated ones as well.

So with your experience are you able to confirm my question please?

Thanks
James Paul

The ones I have examined have had the gauze in the middle section with a gap at both bottom and top, as does the nos cannister I have for the pushrod cover version.
Paul Walbran

Thanks Paul

Appreciate you sharing that.
James Paul

Hi,

I’ve been reading the archives about pcv valves and blue smoke. There’s a lot to get through.

On one of the threads it talks about the oil filler caps and had a photo of removing the bottom of the cap.

I thought I’d find a gauze but mine is different.

Can anyone tell me what should be in the cap?

Thanks


James Paul

James,
I have never taken one apart but the vented caps were classed as a service item and from memory changed at 12000 miles (need to check)

R.
richard b

Hi Richard,

Don't worry, I've checked again and after a run there is no oil around the PCV valve. The new gauze is clean and dry so no oil is being sucked into the engine that way.

Straight after the drive I pulled the plugs and had a look at the valves with my endoscope and can see what looks like oil on the valves. So going to pull the head and see if the oil seals have failed or if there's a head gasket issue.

Oh well at least I can get the radiator sorted whilst I'm at it.

Thanks

James







James Paul

In response to your query I would consider the 'can' should be filled completely but not tightly packed such that coalescing oil vapour is able to freely drain back into the engine, with I seem recall, that two of the stainless scourers were adequate.
Cheers
S G KEIL

Thanks SG
James Paul

Just to update, did pull the head and found a load of oil in the head on the inlet chambers and in the manifold. Rocker gasket was doing its job well so the only place we can think the oil came from was via the pcv valve.

Pistons, head and valves were covered in oil and soot. Cleaned it all up. Found a couple of the water channels needed cleaning out, linked to the old radiator which has had the core replaced. So worth pulling the head.

Found a tiny hole in the pcv rubber diaphragm. Annoying as I replaced that only a few months before. Also the valve wasn’t shutting well, looked dirty. Gave the whole valve a thorough clean and checked for any sharp edges or areas that could allow air leaks. Reassembled and checked by blowing both ways and it seemed well sealed.

Added the new scourers to the fill the oil collector.

Also bought a new oil filler cap and found more air resistance with the new one compared to the old one. Which I assume will make a difference to the air pressure within the engine.

Got it all back together. Fired it up and initially a small amount of blue smoke, but after a decent drive that cleared up.

All seems to be running well for now. Just need to keep on eye on the oil levels to see if this has fixed it.
James Paul

Hopefully youve fixed it James, but oil pooling on the top of the head can be indication of worn rocker shaft, and/or rocker bushes. When worn, oil can be pumped out from behind the rocker bushese faster than it drains away down by the pushrods.
Slide one to one side along the shaft against the spring and feel on the underside of the shaft for a wear step.
GuyW

There wasn’t excessive oil on top of the head, but in the inlet chambers.

It was soaking in fresh oil inside.

They replaced the rocker shaft when is was rebuilt so it should be ok. I hope!


James Paul

Sorry James. I need to read more carefully!
GuyW

That’s ok Guy, still good information to know!
James Paul

James. Don't forget to remember, that these engines are not the close tolerance Japanese or German engines that displaced them. When new, yes, oil 'tight', in most places. Circa 15/20k miles later, and they're burning or dripping a degree of oil. Hence the relatively short oil service intervals.

After 47 years, I've finally accepted that however often, and however much I rebuild my overbored 1275, after a while it still burns and drops a bit of oil but still goes bloody well.

Just part of the 'charm', to see oil staining my expensive red tarmac drive. 🤣🤣🤣



anamnesis

I recently rebuilt the 1971 midget engine. It was the third rebuild in 300,000 miles and I had felt that the rockers and shaft were still OK. The machine shop pointed out that the rocker tips were worn and that the grove was catching the tops of the valve stems, pushing the valves to the side, and causing premature valve guide wear. The rocker tips did indeed have a flat spot that would cause this.

The car had been burning quite a bit of oil, about 700mi/qt. Hopefully the new forged rockers will last another 300,000 miles.
Glenn Mallory

Thats a high mileage for your Midget, Glenn. Well done! Even with rebuilds you must be looking after it well.
GuyW

Message for Guy really as I know you had similar issues to me on my 1098 engine.

Guy do you think some of my rocker bushes are worn?

Here’s two videos:

https://drive.google.com/file/d/1w5o42282fdm3PZd3mDeowyQzXBkja3VT/view?usp=share_link

This video below shows the valves which don’t seem to be flooded in oil.

https://drive.google.com/file/d/1Njtthh0u_pWECs6a9RMsbz4EVk89xzcE/view?usp=share_link

All the oil is flowing down the correct channels.

Hopefully you can see some of the rockers have more oil flow than others. The rocker shaft is new.

Just need to know if that is too much.

I’ve also pull the head to fit the umbrella style 1275 oil seals on the valves stems / guides.

Another question I have which is open to everyone is should I use both the o ring seal which sits in the groove at the top of the valve stem and the umbrella / top hat seal that sits over the valve guide?

My thinking is that the o ring provides some cushioning to the collets, but don’t know for sure.

Seen some say there might be a risk of them hitting each other, but others saying they’ve had no issues using both.

First photo is the valve closed and the second is the valve open flush with the face of the head. The o ring just touches the umbrella seal. I don’t think it will touch when running because I don’t think the valve is flush with the head surface, is it?

Valve guides are new and valve slides smoothly and evenly up and down with no movement.

Thinking of doing both inlet and exhaust valves.

Thanks






James Paul

The umbrella seal is an improvement on the old O ring.

As I understand the aim of the seal is to stop oil being drawn into the cylinder head on the intake stroke so the umbrella should be sufficient. There is also less risk of the 0 ring breaking up and getting into other parts of the engine.
Bob Beaumont

Hi Bob,
Yes also I’ve just thought, does the o ring seal sit in the recess or below on the shaft?
Don’t think I’ll be able to fit the collets with the o ring in the recess?
James Paul

James

Yes the 0 ring sits below the collets so it will be tight!!
Bob Beaumont

James, I couldn't tell if the shaft or rockers were worn from watching your videos. There does seem to be quite a flow of oil from some, but as you say the oil is finding the correct route down and not apparently flooding the valve guide tops.

As regards the oil seals, I am pretty sure the round ones arent supposed to seat in the groove of the valve stem. They should be pushed down the stem to contact the valve guide top, or the top hat seal if you are using both. As the valve opens they will be pushed up the stem a little to end up at the limit of the valve 'stroke'. They then remain in that position where they will act to restrict the oil flow down the stem and moderate the oil loss by suction down the valve guide.
GuyW

James,

Having re-bushed and reamed my pressed steel rockers and fitted them to a new rocker shaft there was far less oil present than in your videos so it would suggest to me that you do have some rocker bush wear.
David Billington

Thanks everyone!
James Paul

If you are not a member of MASC you may not have seen one of my previous articles re rocker shafts.
I sourced heavy duty type from Mini Spares having increased thickness and hence stiffness but unfortunately it was full of swarf requiring end plug to be drilled out. On checking their stock it was found that all shafts had same problem even the replacement sent to me. Buyers beware !!!
Also consider plugging top holes in shaft to ensure that oil is fed to contact zone and does not leak out significantly at upper region where there is no real contact with rocker arm. I also covered this aspect as it was a typical 1960s Mini mod.
S G KEIL

Hi,

I’ve decided to replace the bushes in the rockers for my 1098 engine.

Can someone confirm which ones I need please as Moss catalog only refers to bushes for the forged steel ones and not the pressed steal ones I have.

It should have been done when they rebuilt the engine, but only replaced the shaft.

Thanks

James
James Paul

Can anyone confirm the later sintered rockers CAM 289 fit the 1098 engines as they are available new at various prices incl e bay.

R.
richard b

I’m assuming that nos rockers are already reamed by the factory and ready to go ?

R.
richard b

James,

I can't remember now whether I used the forged rocker bushes or just bought a suitable sized bush from the local bearing supplier as I did them over 30 years ago. The steel backed bronze bushes were readily available in those days in a variety of sizes you just had to order them at the counter and wait a few days for them to arrive, these days they don't seem to be anywhere near as common. I would see if you can find the dimensions of the forged rocker bushes and compare to those in the pressed steel rockers. I remember reading at the time that you couldn't re-bush the pressed steel rockers but as they had bushes in them I couldn't see why not so went ahead and did it anyway. The only issue I had was that a few of the bushes were slightly loose in the rockers so I had to swage the bosses down slightly which as I didn't have a lathe at the time I pressed on a suitably sized socket on either side and that did the job, these days I would turn up a collar to do the job. Anyone know the size of the bushes in the forged rockers?

http://www.minispares.com/product/Classic/Engine/Cylinder_heads/Rocker/2A21.aspx , marked STD, do they come in different sizes. IIRC they need reaming 9/16" after fitting.
David Billington

Spoke to mini spares team and they say the 2A21 bush will fit in the pressed steel rockers but will need to be reamed to fit the shaft.

The sintered rocker CAM289 will fit the standard shaft and doesn’t need to be reamed.

It works out to be cheaper to buy the sintered rocker as the cost for reaming the bushes is about £80 to £100.

I guess I’m a little nervous about trusting that the sintered rocker will fit perfectly.


James Paul

I am 99% sure I used 2A21 in the pressed rockers years before they started before they were listed as forged rockers only, and in those days they were supplied to me by a BMC dealership after consulting a BMC parts book. Makes me wonder if the forged-only reference is the result of Chinese whispers.
Yes, always need reaming, as do B series.

James, I am puzzled about your nervousness about the fit, can you elaborate? The shaft is the same size, length and shaft position the same, and in the original application the contact point with the valve stem is offset from the centreline of the rocker.
Paul Walbran

Hi Paul,

I'm not really sure why. I guess it comes down to would reaming a bush to fit your rocker shaft be more accurate that relying on a standard off the shelf one that should fit any shaft.

I know they should be the same, but experience has told me new parts are not always as accurate.

Turns out the NOS sintered rocker (CAM289) ones on Ebay I found have corrosion in the shaft holes. I asked the seller to check before buying. Glad I did!

So I have gone for new forged steel ones which have the bush and have also been reamed. I got the guy to make sure they all fitted on to a shaft before he sent them to me. He said they were all a good fit.

They turn up tomorrow so will fit them and see if this reduces the oil flow and stops the blue smoke.

If this doesn't work I'm not sure what else it could be. Breather system is now working correctly and not sucking any oil.

Fingers crossed!

James Paul

Just out of interest the new rockers have turned up and thankfully they fit the shaft very nicely. Much better fit than the old ones.

I did notice though that on the adjuster screws they don’t have a hole in the end like the old ones off the pressed steel versions I’ve replaced.

I assume the oil flows down the thread.

Might help reduce the oil flow even more!

I’ll get it all back together soon and report back.





James Paul

Said I would report back and I’m please to say that I’m no longer burning oil!!

I think sorting the whole breather system (new gauze, new pcv diaphragm, new oil filler cap), installing top hat / umbrella valve oil seals and buying new forged rockers to properly fit the new rocker shaft has finally done the job.

Thanks for all the advice, back to happy motoring!

James Paul

This thread was discussed between 11/07/2023 and 06/09/2023

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.