Valve stem oil seals

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GuyWalton
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Valve stem oil seals

Postby GuyWalton » Wed Aug 14, 2019 6:10 pm

I'm just starting the rebuild of the head on my mk1 ariel sq 4 . Valves are ok . Guides are well worn . Looks like valves were replaced but not guides . I will be making my own guides from phosphor bronze and I am considering a valve stem oil seal . As I will be making them myself I can make an audi type oil seal fit . This will stop all oil going down the stem and i'm just a bit unsure as to wether this is a good thing or not . The stems measure 7.8mm [ 5/16"] the audi stem seals are 8 mm so they wont be a tight fit but will be snug . Has anyone done or heard of this mod . The seals will be similar to this .
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paul.jameson
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Re: Valve stem oil seals

Postby paul.jameson » Wed Aug 14, 2019 7:53 pm

I shall be interested to hear how you get on with this. Square Fours tend to run somewhat hotter than water cooled car engines to the detriment of rubber around the cylinder head area. The Mini type O rings on the valve stems of my 1948 4G did not live long, but then oil down the valve guides was not a problem once I had fitted new valves and guides.
Paul Jameson
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.

GuyWalton
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Re: Valve stem oil seals

Postby GuyWalton » Wed Aug 14, 2019 9:21 pm

The hot end of an exhaust valve , in cylinder , runs at 750 c give or take . The cool end , in springs , will be not much hotter than the engine oil . Keeping the oil cool and quickly circulating should help . I have a new morgo oil pump and filter and will also consider fitting an oil cooler now that you have brought the engine heat to my attention . If they do burn then they wont cause any harm as they wont come off .

paul_turner
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Re: Valve stem oil seals

Postby paul_turner » Wed Aug 14, 2019 9:43 pm

Cynric Richardson has fitted them to both the 1938 4g's he restored . one sold at Bonhams auction Stafford a couple of years ago but he still has the other
I have seen the build photographs but can't remember he only fitted them on the inlet valves . I assume they are designed to let enough oil to lubricate the valve stem ?

Knud.Degnbol
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Re: Valve stem oil seals

Postby Knud.Degnbol » Wed Aug 14, 2019 9:46 pm

I can second Paul on this. I also tried to put Mini orings on the valves.They were burned to pieces in very few km. Luckily the pieces didn't fall into the lower engine. I could pick all of it out.

david.anderson
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Re: Valve stem oil seals

Postby david.anderson » Thu Aug 15, 2019 12:15 am

I do believe that the valve stem oil seals are a very good idea. My mk2 shows a lot of oil deposits in the inlet port and there was always traces of smoke from the exhaust of a completely rebuilt engine. Some of the cause is clearly the oil well that is formed in the valve top collar from where the oil drains down the valve stem. I did manage to reduce the oiling by filling the gaps between the split retainers with silicone. If you are going to fit valve stem oil seals make sure that they are Teflon as Teflon will withstand 600F (300C) so it will stand up to the head temperatures of the 4. Viton seals will withstand 450F which makes them marginal for use whereas a standard nitrile seal will only withstand 250F. if and when my new valve guides become worn I will certainly machine the guides to fit valve stem seals.
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Re: Valve stem oil seals

Postby nevhunter » Thu Aug 15, 2019 3:53 am

You can run inlet valve to guide fits pretty close, (they really only have to be free) especially when there's so much oil about. Exhaust guides are a different matter. The need some clearance and on a 3/8 stem it may require .003" If you can get a really good finish ,they will wear a lot less also. Where I can I put a sharp lip on the top end so the oil won't collect there. You can press it in using a tubular piece contacting the ridge half way along it, rather than using the end which is easily damaged once you put the angled edge on it. Nev

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Re: Valve stem oil seals

Postby malcolm.johnson » Thu Aug 15, 2019 11:39 am

Valve springs - fitting.JPG
Valve guides fitted.JPG
When I rebuilt my 1947 iron 4G in 2012 I made my own guides and machined them to suit seals as pictured (early Land Rover I think). I only fitted them to the inlets. I do not ride the bike much but they have covered several hundred miles and it does not seem to use much oil, so I can only assume they are still functioning ok.


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