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Removed my valve seals for exhaust and intake today on #1 cylinder 350 sb with World S/R I-052 cylinder heads. They have umbrella seals the exhaust seal very loose and the intake seal was torn. Neither valve had the upper seal installed. Looking at felpro ss72527 and ss72526 seals for replacement. Why would they not have installed the upper seals. They are .344 valve stems and .575 guide diameter.
Last edited by Dave Witman; Apr 24, 2017 at 05:11 PM.
If by "upper seal" you are referring to is the "o"-ring seals (small black O-rings in the SS72527 picture below). These are all that Chevrolet installed for valve seals, intake or exhaust, on the vast majority of small block heads.
Most of the time these O-ring seals would disintegrate or harden very quickly (~40k or less miles). They did this because the valve spring caps they used would keep most of the oil away from the valve stem. The caps didn't make the seals last longer, they just made them less necessary, to a point.
Except for a pure racing application, I personally would only use Viton® umbrella seals on my SB Chevy heads. A lot of companies offer the Viton® seals including Fel Pro. I would not waste the time to install the O-rings.
The seals you've listed are for .530 guides and may be a problem on your heads. You might want to give Summit or Jegs a call and ask what valve seals they recommend for your heads.
I was surprised to see Fel Pro including the O-ring seals in the kit with the positive seals. They aren't normally used when the positive style seals are installed.
I was surprised to see Fel Pro including the O-ring seals in the kit with the positive seals. They aren't normally used when the positive style seals are installed.
Yes, it seems that Fel-Pro does package some of their sets with both the umbrella and o-ring seals.
I found some interesting, general information on Fel-Pro's site regarding Valve Stem Seals others may find useful.
Valve stem seals are small relative to other gaskets and seals in an engine, but play an important role in lubrication. What makes valve stem seals different than almost every other type of seal? The answer is simple – they are designed to leak. Seals designed to leak may sound counter-intuitive, but the amount and way in which they leak is precisely controlled to achieve a specific goal.
There are two basic valve stem seal designs:
Deflector seals – also called umbrella seals, deflect oil away from the valve stem. They are secured to the valve stem and move with the valve to shield the valve guide from excess oil. Umbrella type seals were commonly used prior to the development of positive type seals.
Positive seals – attach to the valve guide boss and function as squeegees, wiping and metering oil on the stem as they pass through the seals.
As with all of our products, before beginning production, we sample the OE design for every application. Each OE design is tested and benchmarked – we determine the OE material used, the durometer (relative hardness) of the rubber, temperature resistance (to both extreme heat and extreme cold), resistance to common oil types, tear resistance, and leak rate. This type of analysis makes one thing clear, not all valve stem seals are created equal. Visually, a lower-quality seal may look very similar to high quality seal that’s appropriate for a given engine platform, but a lower-quality seal will not work as intended.
Fel-Pro Design
Fel-Pro uses a variety of materials including nylon, PTFE, rubber, steel and synthetic rubber, or some combination of these. A seal with insufficient heat resistance will harden and crack prematurely, which is why Fel-Pro engineers always use the right material for every application. Viton® is used in many Fel-Pro valve stem seals for hotter-running, late-model vehicles. It is often combined with a metal “jacket” or covering that totally surrounds the Viton® positive seal. Viton® offers excellent resistance to both heat (up to 450° F) and abrasion.
Called felpro today and the ss72527 will not work on head with .575 valve guide dia.
Dave, If you can't find a Fel-Pro positive seal that fits your guides, I would just get 2 sets of the SS72526 seals and use them on both the intake and exhaust. The SS72526 seals are deflector (umbrella) seals and should be compatible with your guides, as long as they will clear your springs.
Ford used them on all of their small block engines from the early 70's and never had the issues with valve guide seal failures Chevrolet did with their o-ring seals, for decades. Chevrolet also introduced a Viton, umbrella, deflector seal similar to the Ford on the Vega as well. Back in the 70's & 80's we would use them on SB Chevrolets as well with good success.
I would contact either Fel-Pro or World to see what seal they may have or recommend that will fit your heads... as long as it is an umbrella.
Good luck... GUSTO
Last edited by GUSTO14; Apr 26, 2017 at 08:03 AM.
Reason: syntax
Dave, If you can't find a Fel-Pro positive seal that fits your guides, I would just get 2 sets of the SS72526 seals and use them on both the intake and exhaust. The SS72526 seals are deflector (umbrella) seals and should be compatible with your guides, as long as they will clear your springs.
Ford used them on all of their small block engines from the early 70's and never had the issues with valve guide seal failures Chevrolet did with their o-ring seals, for decades. Chevrolet also introduced a Viton, umbrella, deflector seal similar to the Ford on the Vega as well. Back in the 70's & 80's we would use them on SB Chevrolets as well with good success.
I would contact either Fel-Pro or World to see what seal they may have or recommend that will fit your heads... as long as it is an umbrella.
Good luck... GUSTO
Here....these should work with the .575 guides which I have not seen in years......
I buy all of my seals here.....
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Valve seal selection
