Valve stem seals

ausfordMember

Hi all, i'm seeking opinions on the different types of valve stem seals.

It seems the current trend is to go with the spring loaded elastomer seals that fit on the top of the valve guide after it has been machined, rather than the old style umbrella seal that was tight on the valve stem and rode up and down with the valve.

It worries me that the spring loaded elastomer seals actually work too well, eliminating oil flow to the valve guides.

I have seen engines,admittedly not Clevelands but i don't see the difference as far as valve guide lubrication is concerned, that have suffered considerable valve guide wear in a short space of time after the fitting of this type of seal in place of the old umbrella seals.

My personal thoughts are the old umbrella seals work perfectly well as long as the guides are in good condition. They allow just that small amount of oil past them to sufficiently lubricate the guides.

I have never come across a problem with oil consumption through the valve guides even on high mileage 351C motors.

Why has there been this shift towards these more positive types of seals ?

What experiences have others had with the spring loaded elastomer seals ?

11/20/145:23 PM

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robborrusoMember

Hi Aus,
Hmmm...interesting thought. I have use the teflon/spring loaded jobs for many years now w/o issue. That said, I can't claim to put a lot of miles on my motors. You put forth a logical argument though...

11/20/146:34 PM

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desert_detomaso (Guest)

quote:
Why has there been this shift towards these more positive types of seals ?

Because the stock style umbrella seals are made of rubber that dries out over the years, becomes brittle, falls apart and distributes little pieces of hard, dried rubber into the oil system, where they often manage to get past the oil pickup screen, which leads to jamming the oil pump rotor, which leads to a sheared oil pump drive shaft, which leads to a non-functioning distributor which leads to a dead Pantera sitting in the road.

But it is certainly your choice.

11/20/149:29 PM

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ausfordMember

quote:
Originally posted by desert_detomaso:
quote:
Why has there been this shift towards these more positive types of seals ?

Because the stock style umbrella seals are made of rubber that dries out over the years, becomes brittle, falls apart and distributes little pieces of hard, dried rubber into the oil system, where they often manage to get past the oil pickup screen, which leads to jamming the oil pump rotor, which leads to a sheared oil pump drive shaft, which leads to a non-functioning distributor which leads to a dead Pantera sitting in the road.

But it is certainly your choice.

Yes this is true, but that is a function of the material used, not the way the seals work.

Umbrella seals made from a modern polymer material should not suffer the same fate as the old rubber ones that went hard and broke up as you described.

It is possible to make teflon umbrella seals.

I'm looking for the reason behind the shift in sealing style rather than seal material.

11/21/1412:58 AM

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