Valve Stem Seals in a Twincam

[GrUmPyBoDgEr]

For my part a hypothetical question as I presently run a Zetec engine.
My Twincam memories are of high oil consumption & when, in the past, I looked at the cylinder head & it not having valve stem seals I thought to myself; no wonder, this things an eight cylinder oil pump!
Is there some form of relief to prevent the buckets from pumping?
If not has anyone considered a solution?
I think that the flitting of valve stem seals has been a previously discussed topic but have any of us done this job & done an oil consumption comparison.
The results may be interesting for anyone considering doing a head rebuild.

Cheers
John

[paddy]

Keith Franck, who no longer contributes here, has a forum where he addresses this and other topics.

You might need to sign up for this link to work:

http://autos.groups.yahoo.com/group/vin ... essage/321

Paddy

[JJDraper]

I had my cylinder head refurbed by QED about six years ago and they fitted new guides. I have no idea what they were but they do not appear to allow excessive oil past. No excessive oil consumption or smoky exhaust in the last 50k miles, even on start up. I seem to recall there was some talk about a slight spiral in the guide bore that swept the oil back up and away from the valve head.. Whatever, it seems to work without stem seals. On the other hand I have had cars with stem seals that go hard, letting oil through with the usual smoke.

Jeremy

[Elanintheforest]

I've never had a problem with excessive oil consumption either, and just a puff of blue smoke from the exhaust on start up. A pint every 600 to 800 miles seems to be the norm with my cars.

The Elite is a different story though......


Mark

[john.p.clegg]

I used to have the puff of smoke on start-up but cured that when I rebuilt the engine,after fitting the guides I made up a tool to fit the guides with a tool edge at 45 degrees to chamfer the top of the guide,no longer does oil sit on top of the guide,draining down into the inlet,no reduction in guide length where it matters....

John

[alexblack13]

Hi Guys,
I thought about turning a small groove in the top of the guide and fitting (perhaps even super-gluing in) a small 'o' ring which just slipped over the guide. Would it need doing on them all or just the inlets? I suspect just the inlets?

Might that work?

Ab.... I'll go get my coat again..

[Galwaylotus]

Alex, would that prevent oil getting where it's needed to lubricate the valve stem in the guide? I must admit I'm not familiar with the lubrication system in the Elan head.

[alexblack13]

Well.. All the fords have stem seals with lip /spring..effectively wiping the stems when running and it does not seam to do any harm there. I suspect enough oil still gets to where its needed.

I think that side of things would be ok.. But...? Dont know for sure...

Al'......

[Elanintheforest]

I guess the obvious question is....why weren't they fitted in the first place?

There must have been a reason, and surely this must have been to do with a perceived need for increased lubrication of the valve stems?

Harry Mundy, Richard Ansdale, Mike Costin and Harry Weslake knew a bit about engine design, and valve stem seals weren't exactly new technology in the early 60s.

Mark

[alexblack13]

Dead on Mark. Probably a case for fixing the problem if you are using too much oil. Which no doubt will be down to wear in a guide or guides or perhaps bad fitting valve to guide. I've seen that done. Another new guide needed and more care fitting the valve into it.

Rotten weather up here just now. Wind and rain!

Al' ...........

[GrUmPyBoDgEr]

Hi guys,

an interesting discussion to date & just a couple of things from my side.
My old Mk1 Lotus Cortina was very good on oil consumption; by that I mean that I wasn't checking the dipstick out of anxiety every week.
My question was to those who may have fitted valve stem seals to their Twinc's because I recall this modification being discussed here quite a while ago.
The idea of fitting O-Rings is a scary one to me. Yes I know that they can be used on dynamic applications but they don't replicate the lip seal of a valve stem seal, which are very high tech' bits of kit these days.

Mark,
stop winding me up! You know that I get all nostalgic when I see anything Elite related

Have a good weekend
John

[john.p.clegg]

[quote="Elanintheforest"]I guess the obvious question is....why weren't they fitted in the first place?

There must have been a reason, and surely this must have been to do with a perceived need for increased lubrication of the valve stems?

Harry Mundy, Richard Ansdale, Mike Costin and Harry Weslake knew a bit about engine design, and valve stem seals weren't exactly new technology in the early 60s.

Mark[/quote]
Mark

You seem to forget who commissioned the head and his dislike of opening his wallet....

John

[69S4]

I've never had a problem with excessive oil consumption either, and just a puff of blue smoke from the exhaust on start up. A pint every 600 to 800 miles seems to be the norm with my cars.

The Elite is a different story though......

Mark

Blimy, a litre every 300 miles I've got two stroke bikes that use half of that and they've always got a blue smoke haze following them. They're meant to burn the oil, what on earth is the Elite doing with it?

[rgh0]

To fit in the required valve lift and valve guide length and limit overall engine height there was not much room for a valve stem seal. With the guide to valve stem clearances right you dont need a seal so that is what Lotus decided to do . Yes those guys who designed the head knew a little about engine design.

With a bit of redesign work and shortening the top of the guide and tightening up all the tolerances you can fit in a stem seal if you want. However it is still not really needed if you control the clearances of stem to guide to tolerance and dont worry about oil consumption that was normal in 1965. With Bronze guides and reaming for a tighter tolerance and with modern synthetic lubes you can get essentially no oil consumption down the guides for 60k plus miles before replacement of guides and valves due to wear is needed. Details such as a taper on the guide top also help.

cheers
Rohan