Questions about valve stem seals

Small Block Mopar Engine

  1. SeattleQQ1Fish

    SeattleQQ1Fish FABO Gold Member FABO Gold Member

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    Does anyone have the part number for the MP Viton valve stem seals for my '67 273?
    Should I replace the keepers or just reuse the old ones?
    I'm doing this on the car; what fitting do you all use with air compressors to pressurize the cylinder? How much pressure needed to keep the valve from falling?
    Is it even necessary to use seals on the exhaust valves?

    Thanks in advance for answering more of my many questions. Input from members of this site has been an amazing source of information.
     
  2. Dana67Dart

    Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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    You can always use the rope trick, rather than compressed air.

    Bring cyl to coming up on TDC of compression, feed some cotton cord in to the spark plug hole (not all the way in). Rotate engine a bit more and the valves will stay up. Reverse eng to remove cord when your done. Move on to next cyl in firing order. Rinse and repeat!
     
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    • flyfish

      flyfish C8H18+N2O = :-D

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      Answered what I could in the quote above in BOLD.
       
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      • Krooser

        Krooser Reform School Graduate

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        You'll likely get a puff of oil smoke under certain conditions without exhaust seals. My new race motor won't have them installed.

        Valve locks are ok to reuse.

        If you can't find the correct seals from MP Competition Products has a couple million alternatives.
         
      • Garry in AZ

        Garry in AZ Building a 9 second Valiant FABO Gold Member

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        I made an air fitting by brazing an air hose coupler to an old spark plug body. You don't need much pressure at all. You could probably even J-B Weld them together.
        The rope trick sounds good too, I'll have to try it next time.
         
      • oldkimmer

        oldkimmer FABO Gold Member FABO Gold Member

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        I just bought a shot air hose and a fitting to fit the coupler. The air hose will screw right into the head. Kim
         
      • MOPAROFFICIAL

        MOPAROFFICIAL FABO Gold Member FABO Gold Member

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        Air.
        Rope.
        Best to have a spring mic and shims to set them up... rimac even better...because you wanna know what pressures really are , not just labeled.
         
        Last edited: Sep 27, 2019
      • nm9stheham

        nm9stheham Well-Known Member

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        OP, I'd just go on RockAuto or to NAPA and get the stock Felpro seals. Your engine has plenty of age on it and just getting anything in there will help any oil down the guides! (FWIW..... personally, I use the rope trick.. just makes me feel better that there is no physical way for the valve to drop.)

        BTW, getting the keepers to break free from the retainers can be vexing. One way is to put the open end of a socket on the retainer, and pop it with a hammer to break the keepers free. (I assume you know that you need a spring compressor too.)
         
      • perfacar

        perfacar Well-Known Member

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        just run piston to TDC, starting with #1, no air or rope required!, valve will drop down about 3/16 ". t his way, you can do # 6 same time. # 8 &# 5, same way, #4&7same way, #3 &2 same way. rotate crank in firing order, 1, 8,4,3, job is done.
         
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        • SeattleQQ1Fish

          SeattleQQ1Fish FABO Gold Member FABO Gold Member

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          Very clever, thanks for the idea.
           
        • SeattleQQ1Fish

          SeattleQQ1Fish FABO Gold Member FABO Gold Member

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          Agreed. I'm just going to get Felpros from Napa. I don't think my 52 year old stock 273 needs anything high performance. If it ever does get on the road, It won't see more than a few hundred miles a year.
           
        • nm9stheham

          nm9stheham Well-Known Member

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          Just one possible problem with letting the valve drop onto the piston..... it means you have to compress the spring even more to get the keepers back in.... May work fine if the drag on the new seal can be used to hold the valve up all the way. If it does not work, then you can always apply some rope in the cylinder.
           
        • sireland67

          sireland67 FABO Gold Member FABO Gold Member

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          Head gaskets are cheap, just pull the heads and do them on the bench.
          It is alot less time.
          To hold the valves up, I have used my leak down detector, and the little screw valve spring compressor, complete pain, easier just to pull the heads, plus you can lap the valves in.
           
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          • perfacar

            perfacar Well-Known Member

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            the new seal does hold the valve up , quite well ! I have changed springs this way , took hour and a half total time. from pulling valve covers, to bolting them back on. there's a easy way and the hard way. I chose the easy way. at the races you don't have time to pull heads and do a valve grind, BTW.
             
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            • ClydeT

              ClydeT Member

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              If you use air to hold valves up make sure to secure crank from turning. I used a breaker bar and socket on my harmonic balancer bolt clamped to k frame. The engine will turn when you apply air. Don't want those valves falling into cylinder. Works great for me.
               
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