12G202 Head. Beyond salvage?

[svenedin]

I found this 12G202 cylinder head in my garage. It is very rusty but I cannot see any cracks.

It would be useful for me to have this head refurbished with hardened valve seats for unleaded petrol (my current engine is not modified for unleaded) and the better "Top Hat" valve stem oil seals.

Is this head too far gone to be refurbished. Sadly I think it lived on the garage floor at some stage and got wet over many years.

Stephen

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[ManyMinors]

That looks as if it's been used a s a boat anchor If the 202 head was rare I expect something could be done with it but they are so common and so cheap that I would probably suggest starting with a better one myself

[philthehill]

If you are reluctant to scrap the head it can be salvaged and used again.
Firstly put the head in a citric acid bath at 6 - 1 mixture and leave for awhile. The citric acid will get rid of the rust.
The face of the head can have a light skim. Once the head is cleaned up the unleaded exhaust valve seats can be fitted.
Possibly new valves, guides and springs required but do not replace anything until those parts have been fully examined.
Install top hat oil seals (with the correct valve guides) for the inlet valves, leave off the seals for the exhaust valve stems as the exhaust valves need all the lubrication they can get when unleaded fuel is used.
Even if you go for another head you are going to have to do most if not all of the items listed above.
Good luck.

[svenedin]

Thank you for the guidance.

I have no attachment to this particular cylinder head but I think it is too bad at the moment to be used as an exchange unit for a rebuilt head.

I have a great big tub of citric acid crystals and it is very cheap (I used it descale the washing machine, kettle, shower heads etc) so I may as well give it a soak in a citric acid bath and see where it gets me.

If I was to buy a rebuilt cylinder head they are currently £689.40 (including VAT) with a £125 exchange surcharge included from ESM. That is a lot of money and I would like to try to do this much more cheaply if possible.

[philthehill]

Doing the work on the head shown above will be the cheapest way of fitting a unleaded head to your Minor.
The only major outlay would be the fitment of four unleaded exhaust seats and a light skim of the head. Everything else you can do yourself.

[svenedin]

I gave the cylinder head a wash. It was full of spiders' webs (False Widow Spiders which are resident at my house). It is now in a citric acid bath and I have given it several goes over with a wire brush (by hand). Some of the rust is superficial, already some of the studs are bare metal again after less than an hour. The top section is reasonable, maybe protected by residual oil. The combustion chambers are quite bad. The head must have been flat on the garage floor. I'll give it a few days and see where it gets me.

Stephen

[svenedin]

The rust is coming off. Top looks good but the bottom is quite pitted. Obviously it would need a skim but maybe it's in too poor condition. I don't know.

I am going to take it to a local engineering firm this week. They have agreed to look at it and tell me whether it's junk or worth refurbishing. The valves were rusted into the valve guides which is why I am de-rusting before going any further.

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[philthehill]

That's better
Leave it in the citric acid bath for as long as you can.
Unless the local engineering firm find a crack that head is not for the skip.
That head can be brought back from the dead without too much difficulty and expense.
Phil

[svenedin]

That's better
Leave it in the citric acid bath for as long as you can.
Unless the local engineering firm find a crack that head is not for the skip.
That head can be brought back from the dead without too much difficulty and expense.
Phil

Wonderful. I love it when a bit of effort is worthwhile!

[svenedin]

An engineering firm called me back this afternoon. This one is not local but specialises in Minis so they know the A-series very well. I explained the state of the head (including the boat anchor comment which is very descriptive). They weren’t at all concerned by some pitting. They could take my cylinder head, fully refurbish and convert to unleaded and even paint it at half what ESM charge for a refurbished head.

Tomorrow I’ll take the head to a local firm and see what they say and what they would charge.

[oliver90owner]

I rather smiled to myself when this thread came up. I have a head that sat outside for some time. Certainly not as bad as the one shown but easily cleaned up. It is likely the valve seats will just need recutting, but could be replaced for unleaded quite easily. I gather that the head surface will be too smooth (ground flat on the surface grinder), but I doubt a minor head will complain.

When I knock out the valves, it may well need new guides - I will see - but as a ‘cooking’ head it may not be that important. There is no reason, as yet, why the valves might need anything more than regrinding or refacing. Cost, at present is zilch. I always say “better the devil you know than ……”

[svenedin]

I rather smiled to myself when this thread came up. I have a head that sat outside for some time. Certainly not as bad as the one shown but easily cleaned up. It is likely the valve seats will just need recutting, but could be replaced for unleaded quite easily. I gather that the head surface will be too smooth (ground flat on the surface grinder), but I doubt a minor head will complain.

When I knock out the valves, it may well need new guides - I will see - but as a ‘cooking’ head it may not be that important. There is no reason, as yet, why the valves might need anything more than regrinding or refacing. Cost, at present is zilch. I always say “better the devil you know than ……”

It's quite amazing what will clean up well. I was given quite a lot of parts over 30 years ago. Nobody seemed to want them. I am now pleased that I did not throw those parts away as prices are rising quite steeply. For instance, I was thinking it might be an idea to refurbish a rocker assembly to use with the refurbished cylinder head rather than fitting the worn rockers from the car. I had a feeling I had a rocker assembly in a box and in fact I found two of them. I think one of them will clean up nicely. ESM are asking £179.40 for a refurbished rocker assembly so that is another decent saving. I think all I will need is new springs and a few adjusters and nuts. Both of the rocker assemblies I found are used but they do not seem significantly worn.

[svenedin]

Bad but not unexpected news. My local engineering firm looked at the head and said the pitting on the mating face is too deep. It would require an excessively heavy skim, 40 or 50 thou. I am now on the look out for an unmolested cylinder head!

[Bill_qaz]

Have you looked for oversize thickness head gasket, so you could have your skim and maintain reasonable compression ratio and valve to piston clearance.
I'm sure Phil will know with his many tuning exploits and knowledge.

[svenedin]

Have you looked for oversize thickness head gasket, so you could have your skim and maintain reasonable compression ratio and valve to piston clearance.
I'm sure Phil will know with his many tuning exploits and knowledge.

I think I will just look for a better candidate for refurbishment.

[daveejhitchins]

I've seen similar heads where the 'rust-holes' have been filled e.g. welded, and then skimmed. seems a shame to abandon such a head!

Dave H.

[svenedin]

I've seen similar heads where the 'rust-holes' have been filled e.g. welded, and then skimmed. seems a shame to abandon such a head!

Dave H.

I am not going to throw it away. It may be of use one day!

The engineer thought that it would need so much skimmed off (40 or 50 thou) that an oil way was at risk and also it would upset the compression too much.

Maybe if these get rarely rare in the future it would be worthwhile to try to have the corrosion pits filled with weld but I believe welding cast iron is a special skill.

For now a better used head as a starting point is better value for money.

Stephen

[philthehill]

Looking at your head the face does not look bad enough to warrant a 40 - 50 thou skim.
Your limiting factor as regards the depth of skim is the oil transfer passage from the n/s front of the head to the underside of the rocker pillar and which delivers oil to the rocker shaft. There must be at least 40 thou between the face of the head and oil gallery. This can be easily calculated.
A 40 - 50 thou skim is not that unusual. You have to put spacers under the rocker shaft pillars to keep the rocker geometry the same though. The spacers required are the flat oblong washers that fit on top of the rocker pillars and are held in place by the 3/8" & 5/16" studs.
Just use a good quality copper faced gasket and the gasket will seal without problems.
Phil

[svenedin]

Looking at your head the face does not look bad enough to warrant a 40 - 50 thou skim.
Your limiting factor as regards the depth of skim is the oil transfer passage from the n/s front of the head to the underside of the rocker pillar and which delivers oil to the rocker shaft. There must be at least 40 thou between the face of the head and oil gallery. This can be easily calculated.
A 40 - 50 thou skim is not that unusual. You have to put spacers under the rocker shaft pillars to keep the rocker geometry the same though. The spacers required are the flat oblong washers that fit on top of the rocker pillars and are held in place by the 3/8" & 5/16" studs.
Just use a good quality copper faced gasket and the gasket will seal without problems.
Phil

It was hard to show the depth of the pitting in my photos.

The pitting is particular bad here:

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This is the oil passage that the engineer was worried about:

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[philthehill]

Yes that is the oil transfer passage. It firstly goes vertical from the head face, then horizontal and then vertical to the top face of the head / under side of the rocker pillar.
To determine what is the max skim that can be undertaken you need to measure the distance between the underside of the horizontal passage and the face of the head. To work that out - measure down the vertical passage from the top of the head, then measure the thickness of the head and the difference between the two will give you the thickness of the metal under the horizontal passage. Subtract the 40 thou from that thickness and the remaining measurement will tell you whether you can get away with a 40 0 50 thou skim.
Phil