Lotus Elan

Elan S4 - Plastic/metal sleeve on intake valves

PostPost by: madmaxsiegl » Fri Apr 10, 2020 5:14 pm

Can someone please help understand what those sleeves are for? Found them over all my intake valves.

I cannot find them in the workshop manual and apparently one of them already started disintegrating.

Many thanks in advance!

Max
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PostPost by: nmauduit » Fri Apr 10, 2020 5:54 pm

these are valve stem seals, to prevent oil to go down to the chamber when the valve guides are worn out causing smoke.

There are two main approaches for these oil leaks
- guides should be within specs and the little oil going down the stem is actually good for stem lubrication, this should last a long time and when it smokes because of that the engine actually needs an more complete overhaul than just the seals (also with higher lift than stock it is difficult to impossible to properly install seals)
- modern engines do not use that much oil and thanks to seals the smoke and oil consumption can be reduced

I'm an advocate of the first approach.
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PostPost by: madmaxsiegl » Sat Apr 11, 2020 12:20 am

Thanks for the quick and useful response.

I will also go with the first approach.

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PostPost by: gjz30075 » Sat Apr 11, 2020 8:41 am

Lotus never fitted them, hence they're not found in the workshop manual. Fitting them is not
uncommon during a rebuild of the head.
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PostPost by: knockoffnut » Wed May 06, 2020 8:38 pm

No seals, versus seals has a lot to do with the materials used for the valves and the valve guides. In the early days valves were steel and guides were often cast iron. They needed some oil for lubrication. Bronze alloys didn't stand up to the high temperatures and wear, and seal materials which can live at these temperatures were not yet developed. Now we use 214N stainless steel valves running in guides made from fancy bronze alloys, which wear better, dissipate heat better, and we know how to make seals which usually live in these conditions, so the modern valvestem/guide interface doesn't require as much lubrication. We can add seals which improve performance, and emissions, so we do, as long as the physical space is available at full cam lift. If your engine is already set up for them, then they are definitely worth keeping. Your engine will burn better and run cleaner.
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PostPost by: 2cams70 » Thu May 07, 2020 12:39 am

Some interesting stuff about valve stem material versus valve guide material here.

https://calverst.com/technical-info/val ... and-usage/

I've pulled down crossflow engines in the past fitted with valves having oversize stainless steel stems running in the original cast iron guide and the results certainly weren't pretty.
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PostPost by: Chrispy » Thu May 07, 2020 4:06 am

I've got fancy bronze guides and stem seals. Not a puff off oil smoke now. It used to be like James Bond escaping from the baddy of the week before I had it all fixed up :lol:
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