Viton / PTFE valve stem seals??

[Bob S.]

As I said in another post, I'm planning the restoration of my '66 L-79.

The hope is to use the OE style design valve sealing configuration: a seal on the 11/32" valve stem (in the groove under the keeper groove), and the OE shield under the spring retainer.

I've been unable to find a viton or PTFE seal that replaces the Buna-N (nitrile) rubber OE seal on the standard valve stem. Can anyone point me in the right direction?

Regards and thanks for any help,
Bob S.

[Gene M.]

Re: Viton / PTFE valve stem seals??

Bob, I can't answer your question but I am curious why do you not want the original type material? Maybe Apple Rubber or Parker have an O-ring in Viton. The cross section would not have square sides.

I would think anything with teflon (PTFE) would be a little soft and be difficult to install without marking up the surfaces. Teflon is generally used in a sliding application. The Chevy seals are nothing more than a stationary ring plugging the gap.

[Bob S.]

Re: Viton / PTFE valve stem seals??

Hi Gene -

My interest in Viton or PTFE comes from the frequent advise I've found searching this site to use Viton rather than the OE nitrile valve stem seals........I'm hoping that someone has already been down that road and found / successfully used a direct replacement.

I also spent nearly 20 years engineering diesel fuel systems (pumps, injectors, etc) and was exposed to the inferiority of Buna-N (nitrile) rubber compared to the other materials.

[Duke W.]

Re: Viton / PTFE valve stem seals??

I think you can buy Viton from NAPA - probably Felpro, so check both the NAPA and Felpro online catalogs.

Viton will outlast nitrile at least two to one, so you will probably never have to replace them before the next rebuild. Nitrile valve seals are usually seriously degraded by 75K miles, which increases oil consumption.

PFTE is not a good material for oil seals.

About ten years ago I put together an O-ring kit for Cosworth Vegas. They have a lot of O-rings (but not the valve seals, which are the positive type.) I bought them from a So Cal supplier that serviced the aerospace industry.

I believe the SB valve seals are a standard size O-ring. If someone has the dimensions, you could probably buy them from any industrial O-ring supplier if they can't be found as an OE replacement.

Duke

[Bob S.]

Re: Viton / PTFE valve stem seals??

I think you can buy Viton from NAPA - probably Felpro, so check both the NAPA and Felpro online catalogs.

Viton will outlast nitrile at least two to one, so you will probably never have to replace them before the next rebuild. Nitrile valve seals are usually seriously degraded by 75K miles, which increases oil consumption.

PFTE is not a good material for oil seals.

About ten years ago I put together an O-ring kit for Cosworth Vegas. They have a lot of O-rings (but not the valve seals, which are the positive type.) I bought them from a So Cal supplier that serviced the aerospace industry.

I believe the SB valve seals are a standard size O-ring. If someone has the dimensions, you could probably buy them from any industrial O-ring supplier if they can't be found as an OE replacement.

Duke

Hi Duke - It was after seeing your suggestion(s) about using Viton rather than nitrile that I checked the NAPA / F-M online catalogs (thoroughly, I think) --- but no luck. The only Viton seals I find are the positive type.

So, as I said, I was hoping someone had already been down the road of finding an "off-the-shelf" Viton seal of the same dimensions......

Oh well, I'll have to get an OE seal, measure it and hopefully find a direct Viton replacement.

BTW: In fuel injection durabilty/field tests I saw many times how Viton seals held their durometer long after nitrile seals became hard and brittle.....there's no comparison!

Cheers,
Bob

[Joe L.]

Re: Viton / PTFE valve stem seals??

I think you can buy Viton from NAPA - probably Felpro, so check both the NAPA and Felpro online catalogs.

Viton will outlast nitrile at least two to one, so you will probably never have to replace them before the next rebuild. Nitrile valve seals are usually seriously degraded by 75K miles, which increases oil consumption.

PFTE is not a good material for oil seals.

About ten years ago I put together an O-ring kit for Cosworth Vegas. They have a lot of O-rings (but not the valve seals, which are the positive type.) I bought them from a So Cal supplier that serviced the aerospace industry.

I believe the SB valve seals are a standard size O-ring. If someone has the dimensions, you could probably buy them from any industrial O-ring supplier if they can't be found as an OE replacement.

Duke

Duke-----


The original GM small block valve seals are not an o-ring, per se. The cross section is not round. It's more like a mini-sized flat washer in configuration. It's very possible that an o-ring would work ok, but that's not what was originally used or available in SERVICE from either GM or gasket manufacturers.

[Joe L.]

Re: Viton / PTFE valve stem seals??

Hi Duke - It was after seeing your suggestion(s) about using Viton rather than nitrile that I checked the NAPA / F-M online catalogs (thoroughly, I think) --- but no luck. The only Viton seals I find are the positive type.

So, as I said, I was hoping someone had already been down the road of finding an "off-the-shelf" Viton seal of the same dimensions......

Oh well, I'll have to get an OE seal, measure it and hopefully find a direct Viton replacement.

BTW: In fuel injection durabilty/field tests I saw many times how Viton seals held their durometer long after nitrile seals became hard and brittle.....there's no comparison!

Cheers,
Bob

Bob-----

I don't know of a stock-type small block valve stem seal in Viton material. The Viton valve seals I was referring to in previous posts was the positive-type. It's possible that there are stock-type Viton seals out there but, if so, I don't know of a source.

[Bob S.]

Re: Viton / PTFE valve stem seals??

Oh No! Joe, you've just given Duke a migrane!

After relentlessly advising the use of Viton rather than nitrile OE style valve stem seals, he's gonna have to go back and edit all those posts.....

Seriously, thanks, as always for the input....maybe if someone knows of a OE style viton valve stem seal, they'll chime in......

If not, I'll just go the viton "positive seal" route.

Bob

[Clem Z.]

Re: Viton / PTFE valve stem seals??

you can skip the tin cup and stem seal and use a umbrella seal inside the spring and they are made from viton. just add .032 shim between the spring and the spring pocket in the head to make up for the lost in thickness of the tin cup. this also takes weight off of the valve train for higher RPMs by removing the tin cup. not sure you can even get new tin cups anymore and used ones have a problen with cracking and falling down around the spring. i used to heat the tin cups red hot with a torch to anneal them so they would not crack apart

[Joe L.]

Re: Viton / PTFE valve stem seals??

you can skip the tin cup and stem seal and use a umbrella seal inside the spring and they are made from viton. just add .032 shim between the spring and the spring pocket in the head to make up for the lost in thickness of the tin cup. this also takes weight off of the valve train for higher RPMs by removing the tin cup. not sure you can even get new tin cups anymore and used ones have a problen with cracking and falling down around the spring. i used to heat the tin cups red hot with a torch to anneal them so they would not crack apart

clem-----


You can still get the shields from GM, They're GM #10007818. About 4 bucks each, GM list. As you say, they're just plain 'ol mild steel-----very soft.

[Patrick H.]

Re: Viton / PTFE valve stem seals??

you can skip the tin cup and stem seal and use a umbrella seal inside the spring and they are made from viton. just add .032 shim between the spring and the spring pocket in the head to make up for the lost in thickness of the tin cup. this also takes weight off of the valve train for higher RPMs by removing the tin cup. not sure you can even get new tin cups anymore and used ones have a problen with cracking and falling down around the spring. i used to heat the tin cups red hot with a torch to anneal them so they would not crack apart

OK, so my questions would be 1) where can you easily obtain .032 shims, and 2) what brand/number of umbrella seals would you recommend?

I have to replace valve seals in the 72 I'm working on, and was gonig to ask all about stem seals anyway; someone else beat me to it by a few days.

Patrick

[Joe L.]

Re: Viton / PTFE valve stem seals??

OK, so my questions would be 1) where can you easily obtain .032 shims, and 2) what brand/number of umbrella seals would you recommend?

I have to replace valve seals in the 72 I'm working on, and was gonig to ask all about stem seals anyway; someone else beat me to it by a few days.

Patrick

Patrick-----


1) I don't know where you can get any 0.032" thick valve spring shims. GM used to offer special shims under GM #3731058 for just this purpose. They're discontinued, though, and it's probably just as well since I don't think they were hardened.

However, you can get 0.030" thick shims pretty easily and I think these will do you just fine. You want the HARDENED variety. These are available through a source like Summit branded under the major manufacturers like Crane, Comp Cams, etc. You need shims with the proper ID and OD for the spring pockets in your heads. As I recall, these should be about 0.86" ID and about 1.3" OD.

2) For valve seals you could use GM #460483. These are a little "pricey" though on a per each basis. GM does offer a kit under GM #12511890 which includes 8 GM #460483 seals for the intake valves, 8 GM #10147882 seals for the exhaust valves, and 16 GM #10214034 "o-ring" type seals. This kit GM lists for about 65 bucks and I don't think the exhaust seals will fit your heads and you probably don't need the "o-ring" seals.

You can get a kit of the equivalent of the GM #460483 seals from Summit branded under various major manufacturers. Any of the major brands are fine.

[Clem Z.]

Re: Viton / PTFE valve stem seals??

if you use a "umbrella" type seal the type that moves with the valve inside the spring do NOT use the "O" rings as this will cut down too much on the oil supply for valve stem lubrication. most auto parts will have the "umbrella" type seals

[Joe L.]

Re: Viton / PTFE valve stem seals??

if you use a "umbrella" type seal the type that moves with the valve inside the spring do NOT use the "O" rings as this will cut down too much on the oil supply for valve stem lubrication. most auto parts will have the "umbrella" type seals

clem-----


The GM #460483 are the positive type seals which have spring rings around both the valve stem and valve guide boss. They are similar to
"Perfect Circle" all Teflon seals except they are made of Viton and they do not require machining of the valve guide boss (i.e. they are designed to work with stock OD valve guide bosses). The strange thing is that GM used these seals in conjunction with both the oil shields and the "O-ring" seals. I think they will work quite well without them, though.

Also, GM did not use the GM #460483 on the exhaust valves. For the exhaust valves they used a plastic shield which I believe is an umbrella-type shield although it may be retained in some way to the valve guide boss. I've never actually used these so I don't know too much about them. I think I have some around here somewhere, though. These were also used in conjunction with the oil shields and "O-ring" seals.

For Gen II small blocks (i.e. LT1) things changed. The oil shields and the "O-ring" seals went away. They were replaced by a new-design positive type seal used on all valves, intake and exhaust. However, I don't know if these seals can be installed on earlier Gen I engines without valve guide boss machining or other modifications. "Some day" I'll try to investigate that.