Valve seals- race engine....?

[Caprimaniac]

Some just don't use seals on a race engine- at least drag racing. Road racing and a longer service interval engine might be different.

What kind of seals will give long life and smallest amount of friction?

Nylon?
PTFE?
Viton?
Fluoroelastomer?

I wouod Guess PTFE or Nylon. Any input on this?

Did a search and it did not come up With much...

[Newold1]

Some of that questions answer is going to depend on:
1. engine type as well as NA versus boosted
2. Valve stem and guide material
3. Intake versus exhaust valve?
5. valve stem clearances used
4. Fuel type
6. rpm range

Obviously one answer does not fit all uses.

I do a few of NA V-8 aluminum head engines and I seem to have my best results with Viton seals, bronze guides,QPQ nitrited stainless valve stems and .0015" on intake and .002" on exhaust guide clearances with the springs removed from the exhaust valve guide seal and of course good proper weight oils.

You will probably get a least 20-30 different answers on that question minimum! HA! Have fun choosing!

[PackardV8]

What kind of seals will give . . . smallest amount of friction?

Given race engine spring loads, cam acceleration rates, cycles per second, should valve stem seal friction be accounted for in the decision equation?

[engineguyBill]

I use Perfect Circle PTFE valve seals on all applications that they will fit. Sometimes they will not fit inside small diameter inner springs, such as triple spring applications. On these I use the metal-body seals, such as those available from Pioneer Products and others.

[Newold1]

If this engine is a DOHC small liter size hi-reving racing engine I would get some of your input from successful builders and racers of that particular engine type on this forum.
Hard to argue with success!
Talk to them they will most likely tell you what they are using.

[wyrmrider]

Let's see
PTFE is Teflon brand name
Fluoroelastomer is Viton brand name
recall that there are all Teflon and those with just a teflon ring in rubber which can conform better
I like Viton
new old
I've had stems hard chromed but never nitrided- tell me about it
as I've said many times I use a sunnen hone and od hone the valves and knurl the guides almost all the way through
there are (or were) several materials for the inners of the metal clad seals

[Caprimaniac]

All good input.

Kevin has a point, sure. And application dependent,
I see that.

But yes, na v8 alu heads.... have a set of edelbrock viton seals i might use.
Have original valve seals on a set of edel heads more than 10 years old,and they still work..

I didn't google viton, but i saw at summit they list two kinds of viton: rubber and... was it fluoroelastomer?
Viton is a trademark, right? And at least two formulas....

Got me thinking of hardening the stems now. I can get them nitrided...

Thanks

[wyrmrider]

Viton The name is a registered trademark of The Chemours Company. They are a rubber but I would be very suspicions of on "rubber" that does not also claim to be a fluoroelastomer
Viton fluoroelastomers are categorized under the ASTM D1418 and ISO 1629 designation of FKM.
Viton like EPDM is considerably more expensive than Nitril- regular rubber
I first used Viton for O- rings in Corvairs, VW, Harley- well worth it we could buy them in bulk I put them in little plastic bags for the pushrod tubes etc

[Newold1]

OK here goes me disclosing some of my old close to the vest secrets! Just kidding, a lot of engine builders, head specialists and engine manufacturers have been using these valve processes for years!
QPQ nitiriding is a ferretic salt bath treatment process that can be used on stainless, steel, titanium and certain other metals. When properly done it actually penetrates the metal about .003" and hardens the surface and actually changes some of the properties of the base metal which in the case of certain grades of stainless used in engine valves tends add to valve malleability and ductility. As we all know most aftermarket engine valves use hard chrome stems or certain other hard coatings that are surface additions or treatments. As we know they tend to scratch, gall and sometimes even flake and wear off fairly easily. This QPQ nitirding process will not flake or scratch off and its hardness characteristic tends to polish its surface with use and therefore slow valve guide wear especially in bronze type guides.
I have always been amazed when tearing down heads with these valves the decrease in valve guide wear and the beautiful polished surface on the valve stems. Many major engine manufacturers around the world have switched their uses over to these valves. You can look up and get a quick study on true QPQ nitiriding right here on the net. These are the "black" nitirided valves you see in use today. Their are a few sources in the aftermarket but I use the SI "Black Knight" valves which are produced in this process. My recommendation is "use these valves in quality proper stainless valve type material and and you will never use a chrome stem valve again" JMO

[wyrmrider]

Thanks new old
you referring to flash chrome or hard chrome or both?

[Newold1]

Both types of chroming stems.

There is another characteristic I and others have seen with these QPQ nitrided valves and that is with the added malleable and ductile increases that are imparted to the stainless valve I have had engines with broken keepers, retainers and springs where the valve has dropped just enough to slam the piston hard enough to bend the valve head in some cases nearly 45 to 60 degrees and the head of the valve stays put, the valve drives up into the guide, stays put and the engine does not totally grenade as they sometimes like to do with a dropped valve. In many cases the head needed a little work, the forged pistons had some pretty serious marks and in some cases needed replacing but the big plus was the piston stayed in one piece and stayed in the bore with no cylinder wall, ring or rod damage. I was always amazed when I found this and happy of course but the added malleability and ductility added to the valve stem and head strength was a real benefit. Somewhere in some of my old junk boxes I have a couple of nitrided valves bent like this. I'll attempt to find the valve examples and post some pics of them.

[englertracing]

OK here goes me disclosing some of my old close to the vest secrets! Just kidding, a lot of engine builders, head specialists and engine manufacturers have been using these valve processes for years!
QPQ nitiriding is a ferretic salt bath treatment process that can be used on stainless, steel, titanium and certain other metals. When properly done it actually penetrates the metal about .003" and hardens the surface and actually changes some of the properties of the base metal which in the case of certain grades of stainless used in engine valves tends add to valve malleability and ductility. As we all know most aftermarket engine valves use hard chrome stems or certain other hard coatings that are surface additions or treatments. As we know they tend to scratch, gall and sometimes even flake and wear off fairly easily. This QPQ nitirding process will not flake or scratch off and its hardness characteristic tends to polish its surface with use and therefore slow valve guide wear especially in bronze type guides.
I have always been amazed when tearing down heads with these valves the decrease in valve guide wear and the beautiful polished surface on the valve stems. Many major engine manufacturers around the world have switched their uses over to these valves. You can look up and get a quick study on true QPQ nitiriding right here on the net. These are the "black" nitirided valves you see in use today. Their are a few sources in the aftermarket but I use the SI "Black Knight" valves which are produced in this process. My recommendation is "use these valves in quality proper stainless valve type material and and you will never use a chrome stem valve again" JMO

Hmm what about cr nitride or ti Al nitride