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Does AS have a resident Citroen SM? If not, it does now!


richykitchy
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  • 2 weeks later...

Twice I have tried to buy a project SM and failed, do I regret it yes.

Back in the late 1990s working for a commercial interior design company we had a supplier of bespoke furniture who would turn up at our office in a CX Safari, which got my car mad boss and I attention. He also talked about his SM and as the visits went by we pressurised him into arriving in the SM. I got taken out in the SM and was smitten. I left the company and remain friends with my car mad ex-boss and the supplier with the SM who is Brian Cass.

Brian Cass is a long term SM enthusiast and the SM Columnist for the Citroen Car Club and has a tremendous knowledge of SMs. He is also very approachable to chat SMs.

Brian lists a web site www.citreon-sm.uk solely for SMs.

His email via Citroen Car Club is sm@citroencarclub.org.uk

I also have his phone number and will be happy to pass it on if you PM me.

I can’t help feeling like many columnists he would be pleased to have something fresh to say about SMs.

 

I may not have much SM experience but I do have experience of Sodium filled valves on my Gamma. It only ran for a short while (about 100 miles) after a long period of layup before it snapped a valve head off. My view is don’t chance it and pull the engine apart before trying to start it and replace the valves if they are still sodium. I believe non sodium valves are available. Now I must put our BiTurbo back on the road before anything happens to that and its Sodium filled valves.

IMG_20190531_101105 broad.jpg

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I can’t help thinking that chemists never got to speak to engineers during this experimental* phase of engine design. I think sodium was used as it has low density and good heat conduction, but also low tensile strength and a propensity for exploding in air and water.

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12 hours ago, richardmorris said:

good heat conduction,

It was all about the heat conduction.  Sodium filled (more correctly, sodium core) exhaust valves can be 150°c cooler than non-sodium core valves under extreme engine conditions, making valve burn less likely and reducing the risk of dieseling due to the exhaust valve getting so hot it becomes an ignition source.  Sodium core valves were a way to fix a point-cooling issue, and they worked.

The sodium was never relied upon for any strength in the valve, so essentially it means you have a hollow valve stem (and in some cases, part of the head too), which makes the valve quite a bit weaker, hence they can and do eventually fail.

For road use, completely pointless.  Especially these days with better quality fuels, oils and coolants that mean less soot/grot build up in the combustion chamber and better transfer of heat away from hotspots, by an oil that can cope with being hotter without breaking down.

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Sodium cooled valves are still made for certain racing applications. Although modern metallurgy has provided other solutions for adequate exhaust valve life in road use sodium cooled valves do run cooler and can be made lighter.
4 valve cylinder heads make everything easier on the exhaust valve: two smaller valves are much easier to keep cool than one big valve.

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16 hours ago, cort1977 said:

Didn't vauxhall red tops have these in some applications? Don't recall those having a reputation for valve failure did they? 

Austin A-series 1275GT did too. You know, to overcome the massive* power output. "Stellited sodium-filled exhaust valves" is in the book 

Probably just to try stop the thing from running on after the ignition was switched off. 

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23 minutes ago, PhilA said:

Austin A-series 1275GT did too. You know, to overcome the massive* power output. "Stellited sodium-filled exhaust valves" is in the book 

Probably just to try stop the thing from running on after the ignition was switched off. 

Probably inserted by the motorsport dept for 'homologation' purposes, whether they featured in any engines is anyone's guess.

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17 hours ago, cort1977 said:

Don't recall those having a reputation for valve failure did they? 

Some Sodium filled valves are better designed than others.  They may have had a larger diameter stem, or possibly only a very small amount of sodium in them, which means they can still claim to be sodium filled without reducing the strength of the valve very much.

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On 5/18/2021 at 10:21 PM, cort1977 said:

Didn't vauxhall red tops have these in some applications? Don't recall those having a reputation for valve failure did they? 

The XU9J4 used in the BX 16v (oh yes, and the Mi16, but nobody ever calls it that...) did, too. I remember learning that my car had them years ago, and having no idea what it meant!

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  • 8 months later...
On 2/20/2022 at 9:54 PM, Remspoor said:

about time this thread was revived.

@richykitchy Have you seen this informative website about American SMs?

https://www.seattlecitroen.net/general-information

I had mate, yes thanks. Although I hadn't read all the way through it, which I've now done. Ended up emailing the fella who runs it and he instantly replied seemingly overjoyed that somebody found his page! I pointed out that a lot of people have (this wasn't my first recommendation) and he's delighted! He and his gang have put tonnes of effort into finding out all the little detail differences, and I've promised him I'll check my findings against his data.

Haven't made too much progress with the car itself, sadly. It's VERY rusty (I hadn't realised how much) so really I need to get some weight out of it so I can flip it over and assess properly. It's now living in a new bay which it has all to itself now, though, which is nice!

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  • 5 months later...

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