Valve stem seal question - Ford Mustang Forum
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post #1 of 15 (permalink) Old 11-14-2016 Thread Starter
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Valve stem seal question

Hello,
Using the FelPro engine kit and the valve stem seals come in two sizes. Since I have several gasket sets. I have enough to do the exhaust stems using the taller seals along with the intake valve. How bad/wrong would it be to use the taller seals for both types? Is there a reason for the shorter ones for exhaust?

Thanks in advance!


65 Mustang 289 Coupe
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post #2 of 15 (permalink) Old 11-14-2016
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If you are doing the 65 289, you need to use the umbrella seals, I have only seen them in one length, some rebuild sets have the newer vitron seals for some of the 302's that have the valve guide machined for those seals, they have a metal tension ring around them to hold them on the valve guide, you have to use the proper ones for your heads. If in doubt, post a picture of your heads ,preferably the top without the valve cover on, so we can see the valve guides and the seals. My 2 cts. Good luck.

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post #3 of 15 (permalink) Old 11-15-2016
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Without a picture we don't know for sure what you mean by shorter and longer. Ford did not use what we today call a 'positive' seal which is a lip seal with the little spring around them. Those require your head to be machined since the seals actually fit tightly onto the metal at the base of each valve spring. Instead Ford used little 'hats' that fit on the valve stems and don't physically touch anything else. They are really simple but work surprisingly well.

The Ford parts manual shows 4 seal numbers used on 289s over the years but each engine always used 16 each of the same seal on both intake and exhaust valves. Bob Mannel only shows photos for two different types and I would imagine the other 2 were similar to the early style. The earlier ones were called 'umbrella' seals and were much smaller at the top where they fit on the valve stem and larger at the bottom where they shed the oil away from the stem. The last seal change started with engine change L14 in 1967. Those were flat on top with straight sides that were only a little larger diameter at bottom than top; shaped like a Turkish fez. The description of those later ones says they were 57/64" OD and 23/32" high. The OD given is probably at the larger, bottom, open end. The later 'fez' style 289 seals were also used on 302s.

Using the same seal for exhaust and intake valves is common. Exhaust valve run hotter so they sometimes use a different seal if the intake ones aren't made of rubber than can withstand the heat. If you use good rubber then the same seal can be used on either side. Since the Ford type seals ride on the valve stem they tend to stick to the stem instead of always sliding along the stem length. What rubber you use for those is not as critical as it is for a more modern lip seal that has to seal as it slides.
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post #4 of 15 (permalink) Old 11-15-2016
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Yeah, stick with the good old umbrellas. They make a hard nylon version that you can use on the exhaust if you're worried about the heat.

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post #5 of 15 (permalink) Old 11-15-2016
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Quote:
Originally Posted by oklier View Post
Hello,
Using the FelPro engine kit and the valve stem seals come in two sizes. Since I have several gasket sets. I have enough to do the exhaust stems using the taller seals along with the intake valve. How bad/wrong would it be to use the taller seals for both types? Is there a reason for the shorter ones for exhaust?

Thanks in advance!


Yes there is a reason for long and short black rubber seals. "Some" manufacturers feel the shorter seal ( about 1/2 height helps lubricate the FAR hotter exhaust valve ( heat transfer into the stem) and cool it as well. The intake seal is still long ( like they all used to be) to "shroud" the guide from a large amount of oil that "could be sucked down the intake guide. Other manufacturers still provide " all one size" rubber seals. Standard rubber umbrella seals suffer from heat over time and become brittle , often flaking into pieces that find the oil pump . The other problem is they limit how much cam can be used as the increased lift allows the retainer to pinch it against the valve guide. Cams under .500 lift are "usually " ok.
Randy

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post #6 of 15 (permalink) Old 11-16-2016 Thread Starter
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Hello All,
Thank you for the replies! Yes they are the umbrella type and its a stock 289. I submitted a query to Fel-Pro to see what they have to say as well. However i know that many times the guys in the field know a bit more than the engineers that never leave their office. I'll definitely post what they have to say.
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post #7 of 15 (permalink) Old 11-16-2016
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Quote:
Originally Posted by Gt350HR View Post
Standard rubber umbrella seals suffer from heat over time and become brittle , often flaking into pieces that find the oil pump . The other problem is they limit how much cam can be used as the increased lift allows the retainer to pinch it against the valve guide.
That's where the nylon umbrellas come in. They are better with both of those issues.

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post #8 of 15 (permalink) Old 11-16-2016
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The nylon umbrellas first appeared on Boss 302 engines ( to my knowledge) . They are better for sure but not immune to failure. IMHO they also fit the stem too tight. A seal that positively locates on the valve guide itself is superior in every way. Ford went this way on the 5.0 pushrod engines after 88 or so IIRC

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post #9 of 15 (permalink) Old 11-16-2016
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Quote:
Originally Posted by Gt350HR View Post
The nylon umbrellas first appeared on Boss 302 engines ( to my knowledge) . They are better for sure but not immune to failure. IMHO they also fit the stem too tight. A seal that positively locates on the valve guide itself is superior in every way. Ford went this way on the 5.0 pushrod engines after 88 or so IIRC
Umbrellas are supposed to be tight to the valve stem and travel up and down with the valve. Any seal that goes on the guide will be a positive style seal and won't fit on the guide of older engines without machine work anyway.
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Quote:
Originally Posted by Gt350HR View Post
The nylon umbrellas first appeared on Boss 302 engines ( to my knowledge)...
Thanks for that detail.

I saw from the parts book that the Boss engines used a different seal but didn't know what that the differences were.
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post #11 of 15 (permalink) Old 4 Weeks Ago
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So its 2019, 3 years after this original thread and Iím wondering if Iím getting this right. My stem seals are original and have deteriorated to the point that my oil pump seized and the pump drive shaft sheared. I ordered new felpro seals from auto zone and got 8 intake and 8 exhaust seals (short and tall). Is it correct that the short ones go on the exhaust valve stems? Or, should they all be the same (tall or short)?
Since theyíve deteriorated I canít tell which ones go where other than what autozone parts description says.
Thanks
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post #12 of 15 (permalink) Old 4 Weeks Ago
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Your originals were all one size ( at one time LOL) Now short ones are supplied for the exhaust for reasons mention above. Improvements have been made to improve their lifespan.

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post #13 of 15 (permalink) Old 4 Weeks Ago
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I did mine recently, all one size. No issues.

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23/3/1965 289 Manual Fastback.
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post #14 of 15 (permalink) Old 4 Weeks Ago
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Thank you gentlemen! Just finished putting them in. I used the short ones on the exhaust valve stem.
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post #15 of 15 (permalink) Old 4 Weeks Ago
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Quote:
Originally Posted by Tlkmap View Post
Thank you gentlemen! Just finished putting them in. I used the short ones on the exhaust valve stem.
Here's the "technical truth" about valve stem seals. Their purpose in the first place is two-fold: prevent excess oil consumption, and prevent excessive carbon build-up on valves and in ports.

Engine vacuum is responsible for oil being "drawn" down past the guides, to be burned in the cylinders. Therefore, only the INTAKE valves really NEED stem seals, since the exhaust valve stems "see" almost no vacuum at all. The only oil consumed past exhaust valves is that which can leak down the stems.

This is not to say I use no seals on the exhausts, just 'splainin' what's going on.

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