MF TEA low compression

[MikeyMonster]

Well i got home a day earlier so straight back into it. Excellent tips thanks, i havent read those in any service manuals. I was planning on rotating the engine a few times but i probably wont now and if i do i wont venture into that without keeping those liners held down. If i had and the liner had risen i would of just pressed them back down without realising that id just done damage to a gasket at the bottom of the liner as i just didnt know such a thing existed. That would of being a notorious mess up.

First thing ive done is tilt the head and the problem cylinder definitely has the corresponding shoddy looking valve. Its like a yellow/orange colour and looks as though its top gone as its sitting further recessed in its seat. But i cant see how the top surface of the valve could of come off as it couldnt escape anywhere and its not in the cylinder. Any idea whats caused this or is it just wear and tear? It seems to be the exhaust valve. Also cylinder fours valve is going the same way so i plan to replace it too and i will do the petrol tip for looking for leaks on the other valves.
Heres the problem cylinders two and the normal cylinder threes valves



With the head sitting down the higher stem from the bad valve is clearly noticeable and i suppose that could be one way to check for a bad valve as well before removing the head
The valve in the fourth cylinder on the far left can be seen to be getting higher than the one in the same chamber next to it too. Whereas cylinder 1 and 3 valves are all level.
Oil pressure was fine a while ago but i didnt actually check that after she went poorly.

 

[MikeyMonster]

Things have further progressed- ive taken the two valves out that ,so far, are the ones i want to replace. I dont have a spring compressor so i did what i saw someone do on a video- I put a socket under the valve and placed the head on a flat surface and then i placed a socket on the spring and knocked it with a mallet which allowed the stem to travel up the inside of the socket as the spring went down and that resulted in the retainers falling out. I watched all that behind eye protection.

The seat for the fourth cylinder valve looks ok but there is a potential problem with cylinder twos seat. Hopefully in the photo it can be seen but if not there is a small trough on the top right side of where its being seating where i suppose combustion gases have being seeping through. Due to this valve being small for whatever reason (burnt out?) the seat is actually quite recessed inside the valve chamber and the actual outer seat where a bigger and i assumed new sized valve would seat is unscathed. So im not sure at all what to do with this, for starters perhaps i could wait til i get the new valve and then make a judgement call about its affect or build it up some with my welding electrode.
Or maybe the valves ok and its the seat thats recessed or maybe both?
Some opinion on this would be great. I will also check the head, as suggested, for levelness

View attachment 435221

I should add as an edit that ive compared the two valves ive removed and the one from the worst cylinder is definitely narrower than the one from the slightly worn cylinder four, so it appears some amount of valve shrinkage has occurred

 

[Jerry/MT]

As the seat and the valve wear, the valve moves deeper in the seat from the force of the spring. You will most likely need some machine work done on the head, in particularly the valve seat. I'm not that familiar with the Standard Motors, engine in the TEA-20 but most of these engines have replaceable seats. The seat looks damaged in your photo so it will probably need removal and replacement.

You should probably invest in a shop manual for the TEA series. They are generally available on ebay. et al. It will guide you into what you can do yourself and what you'll need special tools and fixtures for. Additional info that you may find helpful is ton the he Ferguson Enthusiasts of North America(FENA) website. Just google FENA.

 

[MikeyMonster]

Jerry thanks for that. Ive rung up a few machine shops, $90NZ ($60US) per seat installed and they use a universal seat. The other option is a replacement head which ive being offered for about $100NZ with valves etc in situ which seemed very reasonable. Im going to clean her up this morning and maybe swap one of the good valves from another cylinder into her and try the petrol test.

I will also get a caliper reading on them to see just how much narrower this bad valve has become

 

[MikeyMonster]

Ive being getting into to it and im up to the point where the decision on what remedy is to be done is next.
I removed all the valves using the socket technique, i cleaned them up and put the good ones all back in. To anyone else doing this in the future, getting them back in with their retainers without a spring compressor was easy. I just put a socket underneath the head again and pressed down the spring with the retainers sitting in the hole and they would slide down and lock in place, no tools needed.

Examining them the inlet and exhaust valves have the exact same height but their head diameter is different. The specs on new valves is:
Both stems are 7.83mm diameter and the inlet head is 27.95mm and the exhaust is 26.90mm.
I would of thought a bigger exhaust valve made more sense as that would enable better heat dispersal.


The exhaust valve on my damaged valve was 26.00mm and it was at least 0.5mm narrower than the next worse valve.
So this is where i come up with a possible solution as i cant weld it due to it being cast iron and that would also be hard to valve grind later.
Im not keen on paying the money for the new seat insert installation, so what ive tried is putting a used intake valve in the current bad exhaust seat. Its diameter is 27.75 so it sits a little raised of the exhaust seat but with the greater width it would seat over and above and outside the area with the trough and i would then just get a new intake valve for the one ive used in the exhaust seat.

So ive done this and ive done the petrol test and now all cylinders hold the petrol well including the problematic number 2 cylinder.
So the plan at this point is to get a headgasket set and a new intake valve and put her all back together.

Please let me know if theres anything really contraindicated to doing this as a shade tree mechanic type of repair?
I would like to do it to a precision finish but the budget just doesnt allow for it so if this does suffice i will be very pleased

 

[banjodunn]

G'day Mikey definitely a different way of doing it how did you go about grinding the seat face? At $100 I would be looking at the 2nd hand head and be doing the petrol test on it I am not saying that your repair wont work but I would be worried as to the life of the damaged insert you don't want to go through all this and have it last only a couple of months and it may drop the insert with a much bigger repair bill. There is a reason for the old saying of "Do it right Do it once"


Jon

 

[MikeyMonster]

Hi Jon yes i had hoped i had moved far away from that practice of doing improper repairs but it seems there was still some of that left in me.
I dont use the tractor much but when i do its very useful for the jobs i have for its three point linkage, as my only other farm vehicle is my 4X4, or i then have to get in contractors.
I havent touched the seat face yet but im thinking of a grinding tool, the one you spin in your hands and some grinding compound. The other valves i just polished the valves manually and inspected their seats. All the seats apart from two looked really good. Im thinking they are all the seats originally machined in the head in the 1950s so hopefully they cant fall out if this repair goes wrong......

The problem with the second hand head is that its a 500km return trip away so i have no chance to inspect it first but yes i take your point that this is a much higher risk repair. Ive ordered the top gasket kit and the inlet valve so im kind of locked into that now. So when they arrive later in the week il update how i go in terms of putting her back together.

Any other tips on rebuilding/ or concerns on this approach would be most welcome. Cheers

 

[pycoed]

I don't think an inlet valve will last 5 minutes if used as an exhaust. Exhaust valves are usually made of some exotic alloy, some were even sodium filled, to cope with the passage of exhaust gases around 900 deg C. Inlets have nice cool ambient air passing over them. Also seat angles may be different, which will mean you'll never be able to grind a seat by hand, let alone the different diameter...
I'd grind all the other valves in to get nice clean seats & check the valve spring heights - I'd be a bit suspicious if you can compress them easily by hand to get the collets back in. Springs should be cheap enough to replace as a matter of course.
There's no way out of it - that exhaust seat needs to be recut & the valve refaced or replaced. Must be someone nearby with a mill surely?

 

[MikeyMonster]

Pycoed- good points thank you, i will ask them at the tractor place tomorrow whether the valve material on these are different between exhaust and inlet, thats if they know, i wont mention what im doing though, its almost embarrassing writing about it. I take your point about grinding by hand, i have again gone down a shade tree mechanic path as I carefully this morning used a high speed drill attached to the end of the valve stem at the top of the head and being careful not to damage the insert i spun it fast and ive got a seat now which holds petrol very well and the valve is sitting flush with the top of the dome.
So i was feeling rather confident until i read your post

I will ask around about a mill, i know someone who had a small workshop for their bus fleet but they have sold up yet they kept some tools so i may be in luck there. The very important next step i think is to find out about the inlet valves material as you have made mention

 

[pycoed]

I've done a bit of research & the inlets & exhausts have the same seat angle 45 deg, so you're OK there. The valves are the same price too at about £5.40 over here - cheap as chips, so the exhausts may not be special stuff - again good news for you. Springs are £4 each- again nice & cheap.
If you think you can get that seat holding petrol OK, then what I would do is put a new exhaust valve in + a set of new springs & you should be good to go.