Teflon vs. Viton valve seals


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By DANIEL TINDER - 17 Years Ago
I thought I recalled some forum comments about seal type preference, but search came up empty. Can anyone recommend one over the other (from experience) and explain?
By 2DRHRDTP57 - 17 Years Ago
Yes i would be keen to hear from someone on this topic also, i am just rebuilding my Y and have only the rubber seals supplied in the kit and  would like something a bit more durable. Look forward to some posts.
By Ted - 17 Years Ago
The Viton seals are the seals of choice but when going double or triple springs, then they may not fit due to their overall larger diameter and that’s where the teflon seals come into play as they are available in smaller overall diameters.  The Viton seals exert less pressure on the stem itself as compared to its teflon counterpart while still providing a good seal.  Both of these require the top of the guide to be machined so that the seal is secured to the guide and doesn’t move up and down with the valve stem.  This is the ‘positive’ sealing nature of this particular type of seals.  With the Viton seal exerting less pressure on the stem, then the tendency for the seal to come loose from the guide and act like an unbrella seal is also much less than the teflon style.  The Viton seals are also less prone to damage when installing the valves in the heads as long as there is a given amount of oil on them or the plastic covers are used on the stems when installing the seals.
By DANIEL TINDER - 17 Years Ago
Ted;



Are the seals always installed on the dry (machined) guide/boss, or is there some kind of Locktite (?) adhesive used to insure they stay put?
By Ted - 17 Years Ago
DANIEL TINDER (3/16/2008)
Ted; Are the seals always installed on the dry (machined) guide/boss, or is there some kind of Locktite (?) adhesive used to insure they stay put?

Positive type seals are installed dry.  They rely on a friction fit with the machined guide to keep them in place.

 

Bob Garvin (3/16/2008)
I had teflon seals on my fresh 292 it smoked from day 1, I changed to stock rubber seals and it fixed it, no smoke in 3 years.
Sounds like a seal or seals were damaged during their installation.  Teflon seals are very easily torn under their upper spring seal and it's also important that the valve stem covers or protectors be used during their installation to insure that the actual sealing part of the teflon seal is not damaged when being slid down over the valve lock grooves in the stems.  This is just another reason the Viton seals have gained so much favor over the Teflon variety.
By HoLun - 16 Years Ago
Is there any info on what machining is needed to convert to positive seals? and what are the seals off of that will fit the Y after the machining?
By Ted - 16 Years Ago
The positive style valve stem seals I use are of the universal fit in nature and are not specified for a particular application or vehicle.  Besides being available for most valve stem sizes, these seals are normally available in two different guide sizes with one being for a 0.500” fit and the others being for 0.530” guide diameters.  I’ll use the 0.530” for most applications but will use the 0.500” option where triple valve springs come into play.  There are specialized cutters for each size and these cutters simply use changeable arbors that matches the valve stem size.  For the Y, I’ll use a 0.530” seal for the 11/32” valve stem and then machine the tops of the guides just deep enough to insure adequate retainer to seal clearance at full lift for whatever camshaft is being used.  There are other options regarding seals but these cover the majority of what I deal with.  If you're passing through, just stop by and I'll show you the tools and what's involved.
By HoLun - 16 Years Ago
did some searching from the infomation you just posted, I found out what the tool looks like and what the generic seals looks like.

and from the pictures I found, all there is to do is machine outside the guide down to .530 to accept the .530 seal, and the shell of the seal is whats holding it on the guide? This will be easy if I am getting right.



so this is not like the late model engines where there are machined grooves on the guide and uses seals that have ridges on the teflon/rubber/viton that actually lock on to the machined grooves?
By Ted - 16 Years Ago
HoLun (1/27/2009)
so this is not like the late model engines where there are machined grooves on the guide and uses seals that have ridges on the teflon/rubber/viton that actually lock on to the machined grooves?

The grooved guides I don’t deal with very much but they do come as standard equipment on the bronze guides in some of the aluminum aftermarket heads.  The grooves just give some teeth for the seal to hold on to but for the most part, the smooth surface that is a result of machining them yourself is adequate in most instances unless dealing with a particular brand of seal that just doesn’t have much clamping force.  There are also those teflon seals that do require a sealer or adhesive on both the guide and the seal before installing so just pay attention to the specific instructions for the seal that’s being used.