Lotus Elan

Cylinder Head Carbon

PostPost by: vincereynard » Wed Mar 22, 2017 7:48 pm

I've just lifted the head of and it seems to me that it hasn't been touched in years.

This cannot have been overhauled 500 miles ago surely! It doesn't coke up that fast.

p1050061.jpg and


What is the approved method for cleaning the soft alloy, (the exhaust ports are black and sooty as well). Are there products available that will disolved the carbon and leave the ali untouched?
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PostPost by: promotor » Wed Mar 22, 2017 9:01 pm

That looks pretty normal to me. In fact it looks healthy! Easily possible after 500 miles or so.
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PostPost by: vincereynard » Wed Mar 22, 2017 10:49 pm

Really? I'll take your word for it until I get the valves out. That should be interesting.
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PostPost by: rgh0 » Thu Mar 23, 2017 9:00 am

The depth of deposits, especially on the exhaust valve head will tell you. You get a thin black coating very quickly and it does not build up much on the alloy head itself or the inlet valve head overtime. But you get the hard brown deposits on the exhaust valve that continues to build overtime. From the photo I can see the brown deposits on the exhaust valve head. If that is thicker than around 0.05 mm then it is not a recent rebuild IMHO ( or they did not bother to clean up the valve)

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PostPost by: vincereynard » Thu Mar 23, 2017 9:56 am

Thanks for the replies chaps.

Are there any modern techniques to remove the carbon other than the usual physical scrapers / wire brushes etc?
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PostPost by: rgh0 » Thu Mar 23, 2017 10:10 am

I use gasket stripper spray to clean the head face itself including the carbon in the combustion chambers. its designed to remove deposits left by gaskets and sealants but works well to also remove carbon.

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PostPost by: Hawksfield » Thu Mar 23, 2017 10:33 am

Vince

Did you clean the head face for the photo as it looks quite clean. when ever I have removed my head the face is stained around the outside of the fire ring area especial in the middle two cylinders indicating a long time of use.

Hope this examination is not a problem :?:
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PostPost by: promotor » Thu Mar 23, 2017 11:38 am

Remember heads can coke up faster when running rich, or where slight play in valve guides allows a bit of oil through.
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PostPost by: vincereynard » Thu Mar 23, 2017 11:50 am

Rohan,

Like this stuff - http://www.ebay.co.uk/itm/291276456685

This alternative is a bit strange - http://www.ebay.co.uk/itm/281942466559
as it states it will remove any gasket and also "Can be used as a gasket maker or dressing" No idea what that means! "Dressing"- like on a salad? I almost tempted to buy a can to see what it does.

John ,

Hopefully no additional major problems.
I just decided that, considering the rest, it would be silly not to strip the whole engine to check it. It would appear that the head was removed and replaced a short while ago. Whether anything in the way of "lead free" mods were done is another matter. At the least I would expect new valve seats.
Patently the valves themselves were not decarbonised so I have not a lot of hope.

The engine did not smoke or show outward signs of distress. Considering the state of it, it actually ran quite well!

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PostPost by: vincereynard » Thu Mar 23, 2017 11:52 am

promotor wrote:Remember heads can coke up faster when running rich, or where slight play in valve guides allows a bit of oil through.

It is certainly a bit rich, even when hot it has that characteristic rhythmic "hunting" sound.
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PostPost by: ElanDNA » Thu Mar 23, 2017 6:25 pm

Hello all
Look the pictures.
It's a very, very cheap methode to clean.The rest you can give to the pigs.
Sorry it's not a TC in your sense, it's a Audi 5 cylinder TC 20 Valves
with only 100kmiles.
Since this operation I've done 10kmiles with him. The emissions
are perfect. State-controlled last week.
corn.jpg and

forpics.jpg and

p270116_07.5401.jpg and

p270116_07.55.jpg and

p270116_08.4001.jpg and

p270116_08.41.jpg and
It's clean down to the valve seats


Cheers Urs
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PostPost by: vincereynard » Thu Mar 23, 2017 6:51 pm

That is certainly a novel method. Air blast with Corn Semolina ?? I have to admit that is not something that would have occurred to me.

Thanks for the enlightenment!

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PostPost by: KevJ+2 » Thu Mar 23, 2017 7:05 pm

Argh! Semolina...school dinners flashback :shock:
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PostPost by: rgh0 » Thu Mar 23, 2017 7:27 pm

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PostPost by: Chancer » Thu Mar 23, 2017 7:29 pm

But you probably love cous-cous :roll:
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