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  • VG30 valve spring info

    I only had the three sets to test, if anyone has other springs or info, plase share.

    Stock valve springs = 54lbs seat pressure tested
    JWT Spring and shim set = 61bs tested
    JWT set with stock inner spring = 71lbs tested
    Schneider valve springs = 110lbs tested

    To me it seems that the single JWT springs are only marginally better than good stock springs unless you use the stock inner spring with the JWT outer. I'll add the open pressures when I have the data sheet, but for now that's all I can remember. The open pressures were about the same spread.

    I will be putting this information in the new head work page I have been putting off working on for over a year.

  • #2
    why do the jwt springs need shims? for that matter why not just shim the stock springs for more preload and a bit more force?

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    • #3
      They probably use the shim to get the extra pre-load or they found a set that would do the job but were too short. Why not use an easy to find spring and charge a few bucks more for shims than spend the time to find ones that are the right size....yes?
      Attached Files
      http://z31performance.com/forum/viewtopic.php?f=5&t=147

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      • #4
        spring bind

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        • #5
          JK wrote: spring bind
          +1

          Terrible idea putting those wheels on...

          Comment


          • #6
            OK85ZX wrote: I've always referred people to the schneiders... it's what I use on mine as well... and they're cheap, it was around $80 shipped for the whole set from schneider.
            I will be doing that from now on. I will also be adding the stock inner springs to the intake side on my car... I believe the intake valves are being pushed open at higher boost; that would explain the sudden dropoff in power at high RPM.

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            • #7
              i have the schnieder springs, when i rebuild my motor (again bullwinkle?) i`ll have to try the inner spring thing. i`ll let you know what the dyno says

              Exercising my constitutional right to be awesome

              1.5.2. Podium winning cars do NOT need to be running at the checkered flag
              good thing....

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              • #8
                autoworkZ wrote: i have the schnieder springs, when i rebuild my motor (again bullwinkle?) i`ll have to try the inner spring thing. i`ll let you know what the dyno says
                But the schneider springs include both inners and outers to give the 110lbs seat pressure and ~180+lbs open pressure. I would leave them the way they are.

                Addition: This 110lbs may seem high compared to stock but based on what I am hearing and reading it's actually somewhat low for a performance application. Lots of built race engines run 160-180lbs seat pressure or more. Not talking about tiny gins here; these are 1200hp blown V8 engines that see a 50+hp gain at high RPM from stepping up the intake valve spring rate alone!

                Comment


                • #9
                  Jason84NA2T wrote: Addition: This 110lbs may seem high compared to stock but based on what I am hearing and reading it's actually somewhat low for a performance application. Lots of built race engines run 160-180lbs seat pressure or more. Not talking about tiny gins here; these are 1200hp blown V8 engines that see a 50+hp gain at high RPM from stepping up the intake valve spring rate alone!
                  maybe, but they have one giant cam with a fairly soft lobe transition compared to the tiny sohc/dohc cams

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                  • #10
                    Guess I should have went with Schneider.

                    Comment


                    • #11
                      MikeZ wrote: Guess I should have went with Schneider.
                      FYI: I'm leaving the stock inner spring with the JWT spring on your heads when I assemble them. I'm sure you won't have a problem.

                      Comment


                      • #12
                        [quote]Jason84NA2T wrote:
                        Originally posted by autoworkZ
                        i have the schnieder springs, when i rebuild my motor (again bullwinkle?) i`ll have to try the inner spring thing. i`ll let you know what the dyno says
                        But the schneider springs include both inners and outers to give the 110lbs seat pressure and ~180+lbs open pressure. I would leave them the way they are.

                        Addition: This 110lbs may seem high compared to stock but based on what I am hearing and reading it's actually somewhat low for a performance application. Lots of built race engines run 160-180lbs seat pressure or more. Not talking about tiny gins here; these are 1200hp blown V8 engines that see a 50+hp gain at high RPM from stepping up the intake valve spring rate alone!
                        Thats funny, I just so happened to be at the speed shop by my work today returning a -8 hose end and thumbing through a big block book and just so happened to catch that "it is common for many high horse power big blocks to use 300 lbs seat pressure"

                        just ironic that I caught this thread and that book today is all.

                        110lbs makes me feel better about running the redline to 7500.
                        85 Z31 6.0 LSX turbo 766whp/792wtq
                        04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                        Comment


                        • #13
                          [quote]Jason84NA2T wrote:
                          Originally posted by OK85ZX
                          I've always referred people to the schneiders... it's what I use on mine as well... and they're cheap, it was around $80 shipped for the whole set from schneider.
                          I will be doing that from now on. I will also be adding the stock inner springs to the intake side on my car... I believe the intake valves are being pushed open at higher boost; that would explain the sudden dropoff in power at high RPM.
                          Maybe. There's lots of stuff going on in there. You could also be choking on the turbine. Or your throttle body could be too small...

                          I talked with Clark about the springs before buying them, and his feeling was the seat pressure was sufficient for 7000rpm using the S2 profile. By running the single spring rather than inner/outers, valvetrain mass goes down, with a corresponding increase in the springs natural frequency (single spring with higher rate). Where the stock springs get into a float resonance by 7k, the single spring is still able to control the valve. Lastly, running excessive spring pressure only costs power. You want to have just enough to keep the valve against the cam lobe + some extra for longetivity.

                          Why do they require shims? They're Nissan springs from another app. To me that's a plus, as they're going to be made well, of good material, and last.

                          Blowing the valves open?
                          pi()*(0.827")^2 = 2.15 in2 -> 2.15in2*20lb/in2 = 43 lb against back of the intake valve face. Probably not going to blow open.

                          60lb / 2.15in2 = 28 lb/in2 is what it should take at steady state. Though, remember the piston is coming up, compressing the charge, and supplementing the valve spring with chamber pressure against the other side of the valve. So maybe you'll get a little VTEC here. But who cares? You're just putting more good stuff in the chamber, right?

                          What would be bad is if the exhaust valves were EGRing during the intake stroke. But really, that would be more of a turbo problem (backpressure) than a valve spring thing, IMhO.

                          I couldn't help the TB thing.

                          MK
                          It's RWD in reverse.

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                          • #14
                            Hi-RPM...

                            My goals is to have reasonable power in 7500-8000RPM. Can you give more info about the 110lb Schneider valve springs??? Is there any "dual-spring" kit for the VG30E(T)?? Thanks
                            84' 300ZX 2+2 NA (Hardtop)

                            Comment


                            • #15
                              Re: Hi-RPM...

                              BlueThunderZX wrote: My goals is to have reasonable power in 7500-8000RPM. Can you give more info about the 110lb Schneider valve springs??? Is there any "dual-spring" kit for the VG30E(T)?? Thanks
                              Thats what the schnider springs are, dual springs.
                              85 Z31 6.0 LSX turbo 766whp/792wtq
                              04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                              Comment

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