12G202 Head. Beyond salvage?

[svenedin]

I have managed to secure another 12G202 head and the complete rocker gear for £75 which I didn't think was too bad. This particular head still has the valves with "hair clip" type retaining clips which are the older type of valve (the engine on my car has clips like this). The seller measured the head thickness for me at 2.75 inches which suggests it has never been skimmed and the original type valves also suggests that there has been no meddling. I'll know more when I have the cylinder head in front of me but it looks a far, far better candidate for refurbishment. I will not throw away the “boat anchor” head though!

[Bill_qaz]

Are you going to be getting new exhaust valve seats fitted for lead free fuel

[svenedin]

Are you going to be getting new exhaust valve seats fitted for lead free fuel

Yes and new valve guides for the better valve stem oil seals. I have 3 second hand rocker assemblies now and can probably put together a near perfect assembly out of them. My other hobby is watchmaking and clockmaking . My grandfather and great-grandfather were watch maker/clockmakers. I am used to assessing parts for wear which requires examination under magnification. Wear you can actually see or feel is gigantic wear on a watchmaking scale! However watches and clocks move slowly compared to an engine.

[svenedin]

The new to me 12G202 head has arrived. I will unwrap it and have a good look tomorrow. I hope it is a good candidate for refurbishment. I haven't had time to examine it today as it will be an oily mess. Oil is good as it won't be rusty I hope. I have fully refurbished a rocker cover so very slowly jobs get done on my car. I am my own worst enemy because I am too much of a perfectionist and jobs take me a long time.

[svenedin]

The much better candidate for refurbishment head is going off for attention tomorrow. Hardened valve seats, new valves, new valve guides etc. Bottom surface has no pitting and looks good.

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[svenedin]

Somehow I muddled up two threads, this one that I started and another that I rudely gatecrashed when I had intended to be posting in this thread. The reason it happened was that I had searched for "12G202" and the other thread came up first.

Anyway, for completeness, this is the head ready to go back in the car. I have already fitted the heater tap, thermostat and manifold studs.

The changes are:

1) Hardened valve seats for unleaded fuel
2) New valves, springs and valve guides. Newer type of valve guide with groove for "top hat" oil seals.
3) Longer, stainless steel bypass hose stub tube. This enables a new bypass hose to be fitted without taking the head off. An accordion type bypass hose can be fitted without removing the head but they have a reputation for early failure.
4) Stainless steel thermostat housing studs, washers and nuts.
5) Stainless steel heater tap studs.
6) Rocker gasket with cross piece. Less prone to spreading out of shape but can only be fitted with the rocker gear out
7) All new manifold and block studs. Block studs with flanged nuts (no washer needed). Slightly longer studs x2 for where the heater metal pipe bracket attaches enabling the thermostat to be changed without disturbing the head torque. On some engines the heater pipe passes on the manifold side but on mine it is on the spark plug side and crosses over the thermostat housing fouling its removal.
8 Heavier duty, thicker walled rocker shaft
9) Rockers professionally overhauled.

I will start the job of swapping to this new head tomorrow morning.

Stephen

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[svenedin]

Well I've started. Tea break time.

The rocker assembly is yet to come out but to my amazement early indications are that the head is free. I had expected it to be sized solid onto the block and a terrible fight to free it. Instead it seems completely loose.

Bit concerned looking at the inlet ports on the old head as they are very oily.

I've already made tentative enquires with an engine builder about getting a short engine made up if this goes badly and the old bottom end fails to appreciate a new top end! I have 2x spare short engines.

As this thread is long, the reason for swapping the head is that the head gasket is failing gracefully over quite a long time and letting oil out where the oil feed from the block is near the front of the engine. It made sense to me to take this opportunity to fit a refurbished head with hardened valve seats as the head has to come off anyway.

Stephen

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[svenedin]

Well my first attempt at a cylinder head gasket has not gone well.

It does appear that the old gasket was well past it and oil was leaking (photos below).

The old head came off easily, the old studs came out nicely.

I cleaned up the block and was pleased to see that there is no sign of scoring and no lip of wear on the bores.

I fitted a lightly greased copper gasket, copper side up. Went round following the diagram tightening the head nuts and then torqued them down to 40 LbFt.

I started the car, which started first time and warmed up the car static. Then water started leaking down BOTH sides of the engine seemingly coming from the join between head and block.

I am really tired now but I will investigate in the morning. I do have another copper gasket so I could try again but I don't know what I did wrong the first time!

Stephen

Old gasket

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Block

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New gasket

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[philthehill]

Bad luck but these things do happen.
I cannot see anything untoward from your pictured above.
The head gasket is usually marked 'FRONT' which is fitted uppermost and at the front. Is your head gasket so marked?
If as you indicate above you have the better head studs and flanged nuts they should be tightened to 50lbf ft not 40lbf ft You will not strip or break the studs at the higher torque.

[svenedin]

Bad luck but these things do happen.
I cannot see anything untoward from your pictured above.
The head gasket is usually marked 'FRONT' which is fitted uppermost and at the front. Is your head gasket so marked?
If as you indicate above you have the better head studs and flanged nuts they should be tightened to 50lbf ft not 40lbf ft You will not strip or break the studs at the higher torque.

Hello Phil,

Thanks for your kind reply! I think my studs are just ordinary, I just looked them up (they came from Minispares) and the are quoted at 42 LbFt though I have the flanged nuts. I had intended to use better studs than that.

The gasket instructions were copper side up and so I did not look for other markings. There were instructions were not to fill the cooling system with water until ready to start the car which I followed.

I have taken it all apart again and fitted another copper gasket (this one came from ESM, the other from a Mini supplier). I could find nothing obviously wrong.

I have torqued it all down and it is back together but I need to check the valve clearances again and that I think can wait until the morning.

Stephen

[philthehill]

These are the studs I use on all non performance engines:-
https://www.ebay.co.uk/itm/325817517209 ... R4quwejXYg
You can pick them up cheaper than above if you are prepared to search.
Even though used they are perfect for engine rebuilds and can be torqued to 50lbf ft to give that extra nip to the gasket. I have never had a S/H one fail.

[svenedin]

I removed the head and fitted it again with a new gasket. All seemed well until the engine warmed up and then water started leaking again.

To cut a long story short it is not the head gasket and it wasn't the first time either. It is the threaded tube that threads into the head for the bypass. It seems loose and it leaks. I tried wrapping it in PTFE tape and threading back in but it still is not right. The head will have to come off and this needs sorting out by an engineering shop. I will be using those A+ studs after all as it all has to come apart again.......

Stephen

[Bill_qaz]

Can I also suggest while stud removed you clean the block face better than in your picture.
Use emery paper and remove all marks and stains.

[svenedin]

Can I also suggest while stud removed you clean the block face better than in your picture.
Use emery paper and remove all marks and stains.

Will do. I went over with brake cleaner and a scraper. Agree it could be better but I don’t want to scratch it. I think I’ll use a green abrasive pad (like a pot scourer).

It's all rather annoying because the car ran fine with the new head and both gaskets and that is what puzzled me as to where the water was coming from.Then I clearly saw water trickling down from underneath the thermostat housing. I hoped it was the bypass hose but sadly it is not that simple.

At the moment the car is out of action and I can't face taking the head off a third time!!!

Stephen

[Bill_qaz]

I always used emery paper wrapped around a block of wood, you won't damage it, just keep even pressure and move over the surface. You will not scratch it enough to harm it.
Better than any residue causing high spot. Make sure the fire ring area around each cylinder is spotless as you can get it. You can use a wire rotary wire brush in drill, wear eye protection.
Good luck with the next fitting ever one has to learn

[svenedin]

I always used emery paper wrapped around a block of wood, you won't damage it, just keep even pressure and move over the surface. You will not scratch it enough to harm it.
Better than any residue cousi g high spot. Make sure the fire ring area around each cylinder is spotless as you can get it.
Good luck with the next fitting ever one has to learn

True it's all practice I suppose but the actual problem is not the gasket but the bypass stub pipe leaking where it threads into the head. It may all work out for the best because it gives the opportunity to fit the uprated torque studs and I can clean the block up better as well.

Stephen

[svenedin]

Here's a bit of trivia. When I took the studs out I noticed that the nuts are marked with 5 rings. Anyone recognise this? Is it manufacturer's mark? It looks like the Auto Union mark but those rings interlock and I doubt they made Imperial parts.

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[svenedin]

I just might get away without having to go to a machine shop. I cannot measure threads so I do not know what thread the bypass adapter I have is. Whatever it is it does not fit the cylinder head properly (it is too loose) and leaks. It screws in easily (too easily) and is clearly not watertight.

Minispares sell a bypass adapter that they say is 5/8" UNS 16 tpi "Whitworth fine" but they also say some customers fit what is actually a servo adapter that is 5/8" 18 tpi UNF. I have ordered both and will see if they fit. If not, head comes back off and I'll take it to a local engine business.



Stephen

[taupe]

Here's a bit of trivia. When I took the studs out I noticed that the nuts are marked with 5 rings. Anyone recognise this? Is it manufacturer's mark? It looks like the Auto Union mark but those rings interlock and I doubt they made Imperial parts.

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Normally it signifies UNF thread...a part circle on the top face of the nuts also signifies this?

Taupe

[Bill_qaz]

I just might get away without having to go to a machine shop. I cannot measure threads so I do not know what thread the bypass adapter I have is. Whatever it is it does not fit the cylinder head properly (it is too loose) and leaks. It screws in easily (too easily) and is clearly not watertight.

Minispares sell a bypass adapter that they say is 5/8" UNS 18 tpi "Whitworth fine" but they also say some customers fit what is actually a servo adapter that is 5/8" 18 tpi UNF. I have ordered both and will see if they fit. If not, head comes back off and I'll take it to a local engine business.

Phil already told you I previous post
It's whitworth not unf

Stephen