Which Valve Springs with Purple Shaft P4102661?

Big Block A body Tech

  1. Red_Duster

    Red_Duster Well-Known Member

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    Good morning all,
    I cant seem to find the information on spring rates anywhere for this cam. Its the older Mopar Purple Shaft grind. Working with a head manufacturer and exploring some options, but neither they nor I can seem to find the required spring information. I've checked Summit, Jegs and Mancini.

    Anyone running this cam, and what springs are you using?
    Thank you.
     
  2. roccodart440

    roccodart440 Well-Known Member

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    IIRC it used to have this info in the mopar performance catalogs. See if you can get your hands on one of them.
     
  3. rumblefish360

    rumblefish360 So close, yet so far away

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    Is that the 280/.474 cam?
    In there books they have a list of there springs. If you can those particular springs at least MP lists the general specs. From there you can cross reference them to another spring.
     
  4. Red_Duster

    Red_Duster Well-Known Member

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    296/.557
    Ill see if I can track down a book. Not having too much luck.
     
  5. Daves69

    Daves69 FABO Gold Member FABO Gold Member

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    …….
    upload_2019-11-22_12-44-10.png
     
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    • Red_Duster

      Red_Duster Well-Known Member

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      Thanks Dave, that awesome. I can cross-reference that and hopefully find some options.

      Now that prompts another question... I'm just learning valve train stuff, so bare with me, but why different lashes when the duration is the same. Didn't have the cam card, so I set both at .028
       
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      • Dartwizer

        Dartwizer Member FABO Gold Member

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        Found this 20191122_125031.jpg
         
      • roccodart440

        roccodart440 Well-Known Member

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        Is it a .028 int / .032 exh cam spec?
         
      • Red_Duster

        Red_Duster Well-Known Member

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        Based on what Daves69 posted, it looks that way. I assumed that if the lift and duration int/exh were the the same, the lash would be the same. I'm sure the Mopar engineers knew what they were doing, Im really more just curious as I try and understand how all the valve-train works in relation to each other.
         
      • roccodart440

        roccodart440 Well-Known Member

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        I always ran mine .004 tighter than stock cold spec.

        .028 / .032 is noisy and ridiculous lash.
         
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        • 383Duster

          383Duster Well-Known Member

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          Bigger lash spec on the exhaust valve was probably so it could spend more time on the seat for heat transfer
           
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          • rumblefish360

            rumblefish360 So close, yet so far away

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            Spring 2806077 specs in the A engine MP book.
            Anybody have a big block book?
            image.jpg
             
          • rustycowll69

            rustycowll69 Well-Known Member

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            possibly true, maybe partly the reason. I always thought it was because all the exhaust valve train pieces are subjected to more conducted heat so they allow for more expansion by increasing the lash spec.
             
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            • Daves69

              Daves69 FABO Gold Member FABO Gold Member

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            • yellow rose

              yellow rose Doctor of Thinkology.

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              I never ever run any lash that loose. Ever. Back then they used a long, slow lash ramp because springs were marginal and valves were super heavy.

              You can lash them at .022 hot on both sides and be done with it. Anything else is way too loose.

              Once you are confident you have the hot lash set correctly, you can let the engine get cold, and then measure the lash again.

              Whatever it is cold is what it is and from that point forward you can lash the valves cold.

              If you do it this way, you'll end up with a valve lash that is much more consistent. This is because when lashing them hot the engine is actually cooling off fairly quickly. If you are even fairly handy with a feeler gauge, you can test this.

              When you cold check your lash you'll see the valves you lash last are the tightest, because they were the coldest when you got to them. The very first valves lashed will be looser cold.

              Try it.
               
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              • PRH

                PRH Well-Known Member

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                P2806077....... I wouldn’t use them on anything.

                There are tons of better springs available.

                The 557 cam has no unique requirements....... just have whoever is doing the heads use springs suitable for any other flat tappet cam in that lift range.
                140/350-ish, depending on how high you plan on turning it.
                 
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                • roccodart440

                  roccodart440 Well-Known Member

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                  I'd try what Yellow Rose suggested.

                  I've run mine for decades at .024/.028 safely (with aluminum heads) The engines were all run on dynos and checked hot as well. I don't know what the hot lash was but one thing is for certain. You can safely run them tighter than .028/.032.
                   
                • rumblefish360

                  rumblefish360 So close, yet so far away

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                  Have you ever run them tighter?
                   
                • roccodart440

                  roccodart440 Well-Known Member

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                  I've gone .024 on both.
                   
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                  • Red_Duster

                    Red_Duster Well-Known Member

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                    I snugged them down to .025/.028 Saturday. might be in my head but seems a bit quieter than the .028/.032
                     
                  • roccodart440

                    roccodart440 Well-Known Member

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                    Not in your head.
                     
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                    • trapster

                      trapster Well-Known Member

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                      I broke my cam in with the stock 340 valve springs, on my 284/484 cam, then left them in. they seem to be fine. but I also have Rhodes lifters .
                       
                    • rustycowll69

                      rustycowll69 Well-Known Member

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                      I did the same, but I had oem style 340 lifters
                       
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