Lotus Elan

Valve Stem Seals?

PostPost by: hbferrariguy123 » Tue May 07, 2019 12:55 am

For a street engine how important is it to go through the trouble to install valve stem seals? I understand that a clearance of .001 to .0015 without a seal will prevent excessive oil from puddling on the valves, etc... Will that actual work? I hope so because I'm not looking for extra work but I also don't want to skip something I should do while I have the engine apart. Thanks.
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PostPost by: 2cams70 » Tue May 07, 2019 1:27 am

Not very important at all in my opinion and could limit your cam choices. If out of spec. use new correctly clearanced Colisbro guides and you should not have problems for a long time.
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PostPost by: rgh0 » Tue May 07, 2019 11:05 am

Fitting valve stem seals takes a lot of custom work to ensure you have the right clearances between the valve train and the top of the seal and it limits use of high lift cams if you want to go down that route.

Correctly fitted original cast iron guides used to be good for 60 to 80 k miles and will last longer with modern synthetic oils and Colsibro or similar bronze alloy guides will last longer again. By that time you will need to do the valves and seats and followers and sleeve probably so replacing the guides at that time if you ever do 100k miles on the car is no big deal.

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PostPost by: hbferrariguy123 » Tue May 07, 2019 1:47 pm

Great! My Elan's head has bronze guides installed when the PO had the engine rebuilt so I should be good. Onto other stuff!
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PostPost by: potleyu18 » Tue May 07, 2019 4:24 pm

I went to a recent Sussex group organised talk by Gerard Sauer and this query was raised by me as currently undergoing a full engine re build. His response was that it would be beneficial and for the small cost fully justified.
If you need any advice my engine has just been re bored by CTM engineering Contact Charlie on 02085921180 and the head presently undergoing the stem seal alteration rough cost of £60 plus the seals.

Steve
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PostPost by: RichardHawkins » Tue May 07, 2019 6:34 pm

Dear Ferrari Guy,

A gentleman called Keith Franck runs a web site called Vintage Technology Garage, he is in the Sanfrancisco area. I think he runs valve stem seals on his Elan.

Hope this helps,

Richard Hawkins
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PostPost by: 2cams70 » Wed May 08, 2019 2:34 am

Valve stem seals are just a cover up for the real problem which is worn valve guides. If your guide to valve stem clearance is correct you won't have problems. Unlike an OHV engine where you have oil splashing everywhere over the top of the valve stem in a Twin Cam you have the valve sitting under a big umbrella - the follower bucket. Better too much guide lubrication than too little. We are talking about ancient engines here not modern ULEV ones!
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PostPost by: Chrispy » Wed May 08, 2019 3:45 am

My engine was very smokey and it was due to the valve guides. I put in new guides and then had them modified to suit seals. I have the c-type cams which have the lowest lift so wasn't really a drama. Not a puff of smoke now! Very happy :)
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PostPost by: rgh0 » Wed May 08, 2019 10:41 am

I think my response stands on its merits

Provided you have a well built engine with modern bronze alloy guides and the correct clearances and use a modern synthetic oil changed regularly ( rebuild clearance should be bottom of the tolerance range for inlets, middle range for exhaust) you will get a long non smokey life without seals and at the end of that time at maybe 100k miles, seals or not, you will need to do a rebuild for many reasons including guide wear whether you have seals or not. Note your guides will wear faster with steam seals than without due to reduction in lubrication to the valve stems and guides which has its own implications for the life of seating of the valve and life of the guide oil seal. Twincam valve guides are short compared to modern engines using valve stem seals and that has implications.

Seals make it easy to have a non smokey engine on a new build and may keep a poor build smoke free for longer but in the end it does not really get you longer life between rebuilds IMHO. I also doubt more than one or two Elans in the world will do 100k miles in the next 30 years under a single owner so it will be hard to test my proposition.

However based on my experience that a race mile is worth 20 times the road miles in terms of engine wear, I believe I have tested this in the real world with Elan race engines and are confident it will hold up. I have also run my Plus 2 for the 80k miles on the road without seals and bronze guides and the right initial clearances and synthetic oil and the engine does not need a rebuild yet but is getting closer and will need it in the next 20k miles, which will finally give me the excuse to build a big capacity high HP engine for it :lol:

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PostPost by: potleyu18 » Sun May 19, 2019 8:33 am

Update,

Just got the head back from CTM and with the high lift cams i've fitted Piper 285 they said it's not possible to fit seals as with the short guide length and the cam lobe rotation there is not enough clearance for a seal to be fitted.
There comment was that with the new bronze guides fitted and new valves correctly reemed there should not be any oil seepage of any concern, so have taken their advice.

I've had the car of over 20 years and found out through the rebuild the valve stems had been ground to save on shim tolerances. Hence the new valves. Now have a totally rebuilt head which i'm extremely pleased with.

steve
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