BB Chev valve stem seal question....

Grant Eldridge · 08-07-2012, 08:48 PM

I'm trying to source a small OD "rubber" umbrella style of valve stem seal that slips over a 3/8" diameter valve stem and just floats on the stem rather than being fixed to the guide boss. The issue is that I have valve springs with .770" ID so they need to be a smaller OD than the ones I've been able to locate, so that there will be no interference with the springs. These heads are on an assembled engine and have not been machined to accept the aftermarket pressed on types of seal. I'd like to get a part number, manufacturer or supplier that can supply these, or if anyone has some I can buy?
If you prefer to reply privately, you can also reach me at grant4060@yahoo.com, or by PM on this site, thanks!

BillK · 08-07-2012, 09:39 PM

Grant,

If the guide boss has not been machined for a seal, then a small umbrella seal is probably not going to do you any good as it will not go over the guide at full lift. If it does not go over the guide it probably will not do much good.

That being said, the small umbrella seals made for Small Blocks will fit on a 3/8 stem. They are tight but they will work. I have used them on some tractor pulling 4 cylinders and have never seen one break. Not sure if they will fit inside the spring but I can measure one in the AM if you want.

billy leber · 08-07-2012, 09:53 PM

Pioneer 450 seals should work. They measure .750 o.d.

Grant Eldridge · 08-07-2012, 09:55 PM

Thanks, Bill, yes I'd appreciate that! Actually just needs a little oil control from oil running down the stem through the locks, the heads and valves are like new with no wear. The heads should have been set up for the press on seals when they were machined, but.... I had actually trimmed down a set of larger umbrella seals by cutting off the "umbrella" to clear the springs, but they looked pretty rough and I figured someone smarter than me on here would have a better idea. Please let me know, thanks!

BillK · 08-07-2012, 10:19 PM

Grant,
The Pioneer OS450's that Billy mentioned are the ones I was thinking of. The brand really does not matter, any Small Block umbrella from the late 70's should be the same. Your machine shop should have them, I keep a box of 100 on the shelf

Another option is to just put a small block "O" ring on the stem below the retainer. I had a customer years ago that used them on his BB engines and claimed they worked pretty decent. I guess anything to keep the oil from running down the stem would help.

Tom Turner · 08-07-2012, 11:03 PM

If you use GM urethane on the top of the retainer to seal the locks you dont need a seal. The dissassembly of the spring / retainer combo is a little bit of a PIA but it works great.

MAURICE BLENDHEIM · 08-08-2012, 12:29 AM

Grant... I have used the small block o-rings on several different applications and found they work. Had situations with smokey start ups and they were enough to eliminate the problem.

BillK · 08-08-2012, 07:21 AM

Grant,
The Pioneer OS450's I have measure about .720" so they should be ok. Another possibility I thought about this morning is the plastic umbrellas that were used on some of the mid to late 80's 350's that had 3/8" exhaust valve stems. Not sure of the size on those. They are a hard plastic and would not move around as much. Fel Pro number is SS72525 for 8.

Grant Eldridge · 08-08-2012, 09:40 PM

Thanks for all the help, Guys! I'll likely either go with the OS 450's, or the small block o rings. The ports are dry light grey, no sign of oil but just trying to be cautious while I've got the opportunity and the race springs are off. I'm using light ones to break in a new cam. Good time to add a bit better seal for now, then will machine the bosses next time the heads are off the engine.

08-07-2012, 08:48 PM	#1
Grant Eldridge Member Join Date: Jul 2007 Posts: 124 Likes: 0 Liked 0 Times in 0 Posts	BB Chev valve stem seal question.... I'm trying to source a small OD "rubber" umbrella style of valve stem seal that slips over a 3/8" diameter valve stem and just floats on the stem rather than being fixed to the guide boss. The issue is that I have valve springs with .770" ID so they need to be a smaller OD than the ones I've been able to locate, so that there will be no interference with the springs. These heads are on an assembled engine and have not been machined to accept the aftermarket pressed on types of seal. I'd like to get a part number, manufacturer or supplier that can supply these, or if anyone has some I can buy? If you prefer to reply privately, you can also reach me at grant4060@yahoo.com, or by PM on this site, thanks!

08-07-2012, 09:39 PM	#2
BillK Member Join Date: Nov 2005 Location: Waldorf Md Posts: 230 Likes: 12 Liked 30 Times in 17 Posts	Re: BB Chev valve stem seal question.... Grant, If the guide boss has not been machined for a seal, then a small umbrella seal is probably not going to do you any good as it will not go over the guide at full lift. If it does not go over the guide it probably will not do much good. That being said, the small umbrella seals made for Small Blocks will fit on a 3/8 stem. They are tight but they will work. I have used them on some tractor pulling 4 cylinders and have never seen one break. Not sure if they will fit inside the spring but I can measure one in the AM if you want. __________________ Bill Koustenis Last edited by BillK; 08-07-2012 at 10:16 PM.

08-07-2012, 09:53 PM	#3
billy leber Member Join Date: Apr 2009 Location: most places Posts: 211 Likes: 0 Liked 10 Times in 1 Post	Re: BB Chev valve stem seal question.... Pioneer 450 seals should work. They measure .750 o.d. __________________ Billy Leber 1150 SS, 1050 SG, 1962 STK, 185 SC Last edited by billy leber; 08-07-2012 at 09:57 PM.

08-07-2012, 09:55 PM	#4
Grant Eldridge Member Join Date: Jul 2007 Posts: 124 Likes: 0 Liked 0 Times in 0 Posts	Re: BB Chev valve stem seal question.... Thanks, Bill, yes I'd appreciate that! Actually just needs a little oil control from oil running down the stem through the locks, the heads and valves are like new with no wear. The heads should have been set up for the press on seals when they were machined, but.... I had actually trimmed down a set of larger umbrella seals by cutting off the "umbrella" to clear the springs, but they looked pretty rough and I figured someone smarter than me on here would have a better idea. Please let me know, thanks!

08-07-2012, 10:19 PM	#5
BillK Member Join Date: Nov 2005 Location: Waldorf Md Posts: 230 Likes: 12 Liked 30 Times in 17 Posts	Re: BB Chev valve stem seal question.... Grant, The Pioneer OS450's that Billy mentioned are the ones I was thinking of. The brand really does not matter, any Small Block umbrella from the late 70's should be the same. Your machine shop should have them, I keep a box of 100 on the shelf Another option is to just put a small block "O" ring on the stem below the retainer. I had a customer years ago that used them on his BB engines and claimed they worked pretty decent. I guess anything to keep the oil from running down the stem would help. __________________ Bill Koustenis Last edited by BillK; 08-08-2012 at 06:59 AM. Reason: spelling

08-07-2012, 11:03 PM	#6
Tom Turner Member Join Date: Jan 2005 Location: Lake Tapps, Washington Posts: 137 Likes: 0 Liked 0 Times in 0 Posts	Re: BB Chev valve stem seal question.... If you use GM urethane on the top of the retainer to seal the locks you dont need a seal. The dissassembly of the spring / retainer combo is a little bit of a PIA but it works great.

08-08-2012, 12:29 AM	#7
MAURICE BLENDHEIM Senior Member Join Date: Jun 2011 Location: Langley (no igloos), British Columbia, Canada Posts: 567 Likes: 306 Liked 278 Times in 86 Posts	Re: BB Chev valve stem seal question.... Grant... I have used the small block o-rings on several different applications and found they work. Had situations with smokey start ups and they were enough to eliminate the problem.

08-08-2012, 07:21 AM	#8
BillK Member Join Date: Nov 2005 Location: Waldorf Md Posts: 230 Likes: 12 Liked 30 Times in 17 Posts	Re: BB Chev valve stem seal question.... Grant, The Pioneer OS450's I have measure about .720" so they should be ok. Another possibility I thought about this morning is the plastic umbrellas that were used on some of the mid to late 80's 350's that had 3/8" exhaust valve stems. Not sure of the size on those. They are a hard plastic and would not move around as much. Fel Pro number is SS72525 for 8. __________________ Bill Koustenis

08-08-2012, 09:40 PM	#9
Grant Eldridge Member Join Date: Jul 2007 Posts: 124 Likes: 0 Liked 0 Times in 0 Posts	Re: BB Chev valve stem seal question.... Thanks for all the help, Guys! I'll likely either go with the OS 450's, or the small block o rings. The ports are dry light grey, no sign of oil but just trying to be cautious while I've got the opportunity and the race springs are off. I'm using light ones to break in a new cam. Good time to add a bit better seal for now, then will machine the bosses next time the heads are off the engine.