Is there any brand of valve stem seal clearly superior to others?

Engine, Transmission & Driveline

  1. Gerald Morris

    Gerald Morris Senior Member

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    Greetings Moparians!

    Havig noticed a slow increase in the volume of oil smoke at start-up, I'm inclined to suspect that the valve stem seals on the 516 heads Mathilda currently runs should be replaced. I would like to do this before Summer Solstice ideally, and pray this will suffice to keep those heads working well until I'm ready to put some well rebuilt 915s on as an upgrade.

    I DO NOT want to break the seal integrity of the head gaskets for any trifle! I plan to research first the best method of replacing the valve stem seals with the heads in situ, pick a good weekend for it, then do the job. I'll take compression readings Before and After as a means of quantifying success.

    This being said, the Question arises: Is there any brand of valve stem seal for Mopar B/RB stock heads which clearly distinguishes itself above others in quality? I currently possess a full set of Fel-Pro seals as part of a head gasket set purchased about 1 year ago, in anticipation of some head work, with the Babushka's observation of start-up fumes then. Will these suffice for the nonce, and should I use them thus: reserving the 915s for better quality valve stem seals?

    If so, whose product would be best? I need to start collecting parts for those 915s well matched to our purpose anyway. Hughes offers material which we deem MOST interesting and in close keeping with the design philosophy we wish to follow: plenty LOW END torque for urban driving and to best utilize the 2:76 ratio rearend on the highway. (I've NEVER had that 383 turning faster than ~4000 rpm in the 5 years we've had it, and see little point in doing so. We'll let folks with the need for that kind of performance do so with our blessing, but its not for us with this car.)

    Being so inclined, I suspect stock seals should do, but saw some references to silicone seals and such, which appeal to my liking for longevity. If any of you Most Learned Moparians favor a special brand/model of valve stem seal, we await your wisdom!
     
  2. Trace 300 Hurst

    Trace 300 Hurst Professional Tinkerer FCBO Gold Member

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    To simply replace seals with the heads on, you're restricted to an OEM style "umbrella" seal. This is opposed to the higher performing "Viton" or "PC-Type" seals that require machining the top of the valve guide, like these:
    hrs-93310_w.jpg

    Having said that, the OEM Fel-Pro seals will give you years and years and years of service, no problem.

    As for checking compression Before and After, valve seals have nothing to do with the sealing of the combustion chamber, i.e. a compression check. That is the job of the piston rings and the intake and exhaust valve/seat mating surfaces. Valve seals are only to prevent an excess amount of oil from running down the valve stem and into the combustion chamber (intake valve) or into the exhaust port (exhaust valve). So, you can replace valve seals and end up with the same smoke situation if it's worn piston rings.

    Further, it's often worn out valve guides/valve stems that strongly contribute to excess oil running down along those surfaces, and valve seals will do little to solve that issue. Why? Valve seals don't really "seal". They're just umbrellas that divert most of the oil flying around inside the valve covers away from the valve stem/guide area.
     
    Last edited: Apr 17, 2021
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  3. Trace 300 Hurst

    Trace 300 Hurst Professional Tinkerer FCBO Gold Member

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    Now you need to start asking about favored methods of replacing seals in situ. I'll stay out of that particular fray, except to say this:
    Regardless of what method you pick to hold the valves in place when removing the keepers and springs--compressed air or the low-tech "clothesline" version--you MUST disconnect your battery just in case, somehow, a tool gets across your starter solenoid and rolls the engine over even for a millisecond. That would be disastrous to the procedure as your valves disappear into the cylinders.....
     
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  4. CBODY67

    CBODY67 Old Man with a Hat

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    No real need to head for the highest-dollar alternative in valve stem seals. Anything of OEM quality will be fine.

    As mentioned, if the valve guide/stem clearance is still toward the bottom end of the clearance spec, the "deflector" orientation of the umbrella asals works just fine AND was recommended by my late machine shop operative. Consider that even the Chevy o-ring seal is probably the least expensive seal as it only seals when the valve is at max lift and port flow is at its highest.

    When we were discussing these things decades ago, I asked about the PC-style seal as it had been purported to be "the best" in a race engine build back in the later 1960s. His reply was that as they scraped the stem of oil, very little oil would get into the guide, which meant "less lubrication" and "more guide wear", which is not good or desired in a non-race motor that we would like to see go 80+K miles between valve jobs.

    Here's a long-term recommendation/source for B or RB gaskets/seals. Mopar Performance used to sell an "Engine Tear Down" gasket set. The advertised orientation was that it could be used for those "class winner teardowns" at high level drag racing events, where the winner has to expose what's in their engine in order to validate the legallity of their engine. It included everything from head gaskets to an oil pump pickup tube gasket. Back then, it was about $100.00 USD. I was not expecting much, but it had every gasekt to rebuild the motor. Even with, back then, steel head gaskets.

    I seem to recall that 454 Chevy valve stems are the same diameter as B/RB valve stems and also came in a red/orange silicone for some applications. My machine shop guy would trim their length with a sharp razor blade for Chrysler B/RB heads. To me, THAT would be the only upgrade I would consider and they were OEM, too, which might decrease the cost a bit.

    If the guide wear is where the oil is coming from, the silicone might be a bit more fogiving as the stem moves laterlally within its casting, possibly?

    As for changing, you'll need a hand-tightened valve spring compressor to compress the valve spring and remove the two locks on the retainer. Once those things are done, then other methods can help keep the valve stem up (compressed air in the cylinder or other mechanical means) to lightly oil the seal/stem for installation. Then re-install the spriing, retainer, and locks. Being careful to get the locks back in their grooves on the valve stem fully before releasing tension on the valve spring. Might take a few times to get things to work smoothly?

    Be sure to protect the upper fenders and anodized aluminum trim! Might be best to use a bore scope to inspect the cylinders to look for oil-washed areas on the piston tops, for good measure.

    Most oil at start-up, especially overnight, might well be from valve stem/guide areas. In the middle 1970s, some OEM engines did not use seals on the exhaust valves, so they always smoked for a few seconds upon startup after they got some miles on them. IF that might help explain or justify things?

    Just my thoughts (and those of my late machine shop operative/mentor) and observations,
    CBODY67
     
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  5. Gerald Morris

    Gerald Morris Senior Member

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    XLNT! Then those little umbrellas should do just fine! Good to know.

    This shouldn't be much of the case, as 1.) The compression had checked out good a couple yrs ago, ranging from ~125 to 146 psi, with the middle cylinders, (3,5,4.6) all showing 140+psi, while the end cylinders (1,7,2,8) all rated the low readings down from 125-135 psi. I figured the lower compression may have resulted from the head gaskets having a little erosion on the ends, though I KNOW nothing yet, except the vacuum at 500 rpm, my curb idle still pulls at 17 inches once the motor is warmed up.

    2.) The engine doesn't smoke once its warmed up. The rings still seal fairly well. I suspect they HAVE worn, sure, after 55 yrs and all, but my exhaust remains clean aside from startup. That's what gave me the valve stem "seal" bug. The engine shows textbook symptoms of that. A compression check helps assess the state of the block, the piston rings and possible valve damage, but yes, if its ONLY the stems and seals, I shouldn't expect any change from replacing them.

    This point is well worth keeping in mind, and I thank you for your input!
     
  6. Gerald Morris

    Gerald Morris Senior Member

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    AMEN!!! I think the "rope" method most prudent for this sort of job. I want something SOLID supporting those valves while those keepers are off! Yes, the starter MUST BE TOTALLY DISABLED while the work is in progress.
     
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  7. Gerald Morris

    Gerald Morris Senior Member

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    As nigh ALWAYS, I save YOUR thoughts for Last because they're BEST. I think a decent fiber optic camera might be worth getting soon, before I so much as take a single 7/16" wrench or socket to the valve covers even. I would dearly love to see the pistons and cylinders a bit in the motor I'm actively using. Silicone seals also appeal a bit, provided I don't need to disturb the head gaskets to use them. I suspect I'll use what Fel-Pro provided if/when I do this job. A good valve spring compressor is on the Tool Shopping List regardless of this job, as they're too useful for too many things to do with heads and valves.
     
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