It's not necessary that they stick down on the head. Their real purpose is
to stop the oil that would otherwise be running down the valve stem and on
thru the guide. As they get old and hard the seal at the valve stem is what
fails. They work by shedding oil, not sealing the guide. Small block
chevys use a little rubber o-ring that acts like a gasket that seals the
stem to the valve spring retainer, the inverted metal cup on top of the
valve stem. Doesn't come close to the head and the valve stem doesn't move
inside the valve seal..
Steve
"William Oliveri" <wuji@bigvalley.net> wrote in message
news:bunq92$k2m2d$1@ID-193866.news.uni-berlin.de...
> All of mine are the same size. They are Fel-Pro Premium Quality NYLON the
> box says.
>
>
> So the "umbrella" effect is that at the down position of the valve the
seal
> rests on the head and at the up position the seal has enough depth or
> length to shield oil from getting in. Is that how it works?
>
> When I looked at mine it seemed they were about half way up the stem.
When
> I checked my plugs it looked like almost every one had a wet look around
the
> base of the threaded part of the plug. Someone else mentioned that if an
> engine overheats it will ruin the valve seals. What happens to them that
> makes them not function properly any more? Does the heat cause them to
> shrink thus loosing the umbrella effect?
>
>
> Thanks,
>
> Bill
>
>
>
>
>
>
>
> "L.W. (ßill) ------ III" <----------@***.net> wrote in message
> news:400F68D0.B0529614@***.net...
> > Hi Bill,
> > That's the way they are supposed to ride, kind of like an umbrella.
> > The bigger seals, if there is a difference will be the intakes and be
> > soft enough to suck around the guide when compressed, the exhaust seals
> > may brown rather than black. Of course, slide them all the way down for
> > installation.
> > God Bless America, ßill O|||||||O
> > mailto:-------------------- http://www.----------.com/
> >
> > William Oliveri wrote:
> > >
> > > I'm getting a compressor by this weekend to get these changed.
However,
> a
> > > couple of days ago, when I was trying to change the seals, I noticed
the
> old
> > > ones were riding up on the valve stem. I'm curious what would cause
> them to
> > > ride up like that. Did they shrink or expand? Is that a common
> occurrence
> > > and also, I noticed the new ones don't have a means to "hold" or "tie"
> them
> > > down. What is the theory behind how the valve seals seat themselves
> > > properly and then remain in the proper position thereafter?
> > >
> > > Thanks in advance,
> > >
> > > Bill
>
>

 

It's not necessary that they stick down on the head. Their real purpose is
to stop the oil that would otherwise be running down the valve stem and on
thru the guide. As they get old and hard the seal at the valve stem is what
fails. They work by shedding oil, not sealing the guide. Small block
chevys use a little rubber o-ring that acts like a gasket that seals the
stem to the valve spring retainer, the inverted metal cup on top of the
valve stem. Doesn't come close to the head and the valve stem doesn't move
inside the valve seal..
Steve
"William Oliveri" <wuji@bigvalley.net> wrote in message
news:bunq92$k2m2d$1@ID-193866.news.uni-berlin.de...
> All of mine are the same size. They are Fel-Pro Premium Quality NYLON the
> box says.
>
>
> So the "umbrella" effect is that at the down position of the valve the
seal
> rests on the head and at the up position the seal has enough depth or
> length to shield oil from getting in. Is that how it works?
>
> When I looked at mine it seemed they were about half way up the stem.
When
> I checked my plugs it looked like almost every one had a wet look around
the
> base of the threaded part of the plug. Someone else mentioned that if an
> engine overheats it will ruin the valve seals. What happens to them that
> makes them not function properly any more? Does the heat cause them to
> shrink thus loosing the umbrella effect?
>
>
> Thanks,
>
> Bill
>
>
>
>
>
>
>
> "L.W. (ßill) ------ III" <----------@***.net> wrote in message
> news:400F68D0.B0529614@***.net...
> > Hi Bill,
> > That's the way they are supposed to ride, kind of like an umbrella.
> > The bigger seals, if there is a difference will be the intakes and be
> > soft enough to suck around the guide when compressed, the exhaust seals
> > may brown rather than black. Of course, slide them all the way down for
> > installation.
> > God Bless America, ßill O|||||||O
> > mailto:-------------------- http://www.----------.com/
> >
> > William Oliveri wrote:
> > >
> > > I'm getting a compressor by this weekend to get these changed.
However,
> a
> > > couple of days ago, when I was trying to change the seals, I noticed
the
> old
> > > ones were riding up on the valve stem. I'm curious what would cause
> them to
> > > ride up like that. Did they shrink or expand? Is that a common
> occurrence
> > > and also, I noticed the new ones don't have a means to "hold" or "tie"
> them
> > > down. What is the theory behind how the valve seals seat themselves
> > > properly and then remain in the proper position thereafter?
> > >
> > > Thanks in advance,
> > >
> > > Bill
>
>

 

It's not necessary that they stick down on the head. Their real purpose is
to stop the oil that would otherwise be running down the valve stem and on
thru the guide. As they get old and hard the seal at the valve stem is what
fails. They work by shedding oil, not sealing the guide. Small block
chevys use a little rubber o-ring that acts like a gasket that seals the
stem to the valve spring retainer, the inverted metal cup on top of the
valve stem. Doesn't come close to the head and the valve stem doesn't move
inside the valve seal..
Steve
"William Oliveri" <wuji@bigvalley.net> wrote in message
news:bunq92$k2m2d$1@ID-193866.news.uni-berlin.de...
> All of mine are the same size. They are Fel-Pro Premium Quality NYLON the
> box says.
>
>
> So the "umbrella" effect is that at the down position of the valve the
seal
> rests on the head and at the up position the seal has enough depth or
> length to shield oil from getting in. Is that how it works?
>
> When I looked at mine it seemed they were about half way up the stem.
When
> I checked my plugs it looked like almost every one had a wet look around
the
> base of the threaded part of the plug. Someone else mentioned that if an
> engine overheats it will ruin the valve seals. What happens to them that
> makes them not function properly any more? Does the heat cause them to
> shrink thus loosing the umbrella effect?
>
>
> Thanks,
>
> Bill
>
>
>
>
>
>
>
> "L.W. (ßill) ------ III" <----------@***.net> wrote in message
> news:400F68D0.B0529614@***.net...
> > Hi Bill,
> > That's the way they are supposed to ride, kind of like an umbrella.
> > The bigger seals, if there is a difference will be the intakes and be
> > soft enough to suck around the guide when compressed, the exhaust seals
> > may brown rather than black. Of course, slide them all the way down for
> > installation.
> > God Bless America, ßill O|||||||O
> > mailto:-------------------- http://www.----------.com/
> >
> > William Oliveri wrote:
> > >
> > > I'm getting a compressor by this weekend to get these changed.
However,
> a
> > > couple of days ago, when I was trying to change the seals, I noticed
the
> old
> > > ones were riding up on the valve stem. I'm curious what would cause
> them to
> > > ride up like that. Did they shrink or expand? Is that a common
> occurrence
> > > and also, I noticed the new ones don't have a means to "hold" or "tie"
> them
> > > down. What is the theory behind how the valve seals seat themselves
> > > properly and then remain in the proper position thereafter?
> > >
> > > Thanks in advance,
> > >
> > > Bill
>
>