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| Would you intend to buy new lightweight springs? |
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| Total Votes : 6 |
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Coco_Lev
Joined: 04 May 2020
Posts: 104
Location: France
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 Posted: Tue Oct 14, 2025 6:06 am Post subject: Lightweight valve springs interest survey |
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Hi folks,
I have been working for some time on the replacement of valve springs.
Planning for direct replacement springs to fit original retainers. They are made of dual (cylindrical) springs with variable pitch for inner spring (for rejecting the resonance frequency to higher revs). Moreover the original load / deflection behavior is ensured (verified).
Old OE springs were the stiffer springs produced among all the various batchs more recently produced. I propose to stick to these specs to avoid unnecessary wear at follower / cam contact surface.
The benefit of the designed springs is in the wire grade used, ready to handle about 30% higher stresses. As a result, the springs are 21% lighter, and have a 10% higher resonant frequency. The combination of these two improvements allow for a safe max 400RPM increase from similar past studies. Springs will also exhibit lower sag for better long term performance.
If we can collect sufficient interest for these and the batch can be made, the price would be around 140€ the set of 8 pairs (16 springs overall), some small discount could evenly be expected for the very first units.
Looking forward for your interest,
Thanks
Corentin
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Last edited by Coco_Lev on Thu Oct 16, 2025 1:59 am; edited 1 time in total |
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morghen
Joined: 21 Jan 2005
Posts: 9082
Location: Romania
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| Posted: Tue Oct 14, 2025 5:13 pm Post subject: |
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I'm interested.
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peterld
Joined: 10 Dec 2006
Posts: 978
Location: Noosa Heads QLD Australia
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| Posted: Tue Oct 14, 2025 9:37 pm Post subject: |
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Count me in.
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Raize
Joined: 18 Sep 2013
Posts: 398
Location: Scotland
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| Posted: Fri Oct 17, 2025 6:52 pm Post subject: |
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| That’s cool, i would be interested in raising RPM limit a bit if i was ever building an engine. It seems like the kind of thing that would sell slowly over a long time as and when people are doing engine rebuild rather than the latest must-have bolt on upgrade. |
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safe
Joined: 18 Mar 2017
Posts: 687
Location: Sweden
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| Posted: Fri Oct 17, 2025 9:51 pm Post subject: |
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Valvesprings are NLA as I can see it, at least the outer springs.
So springs I think would be a good addition to the rare 924 parts.
I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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Cedric
Joined: 27 Aug 2004
Posts: 2761
Location: Sweden
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| Posted: Fri Oct 17, 2025 10:05 pm Post subject: |
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| safe wrote: | Valvesprings are NLA as I can see it, at least the outer springs.
So springs I think would be a good addition to the rare 924 parts.
I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too. |
Maybe Corentin can help you with the analysis of that to see what you need with the boost+RPM, he have put together a model for valve train analysis that might be possible to use.
I wish these were available when i put my engine together, might get a set anyway for future use 
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safe
Joined: 18 Mar 2017
Posts: 687
Location: Sweden
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| Posted: Fri Oct 17, 2025 10:22 pm Post subject: |
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| Cedric wrote: | | safe wrote: | Valvesprings are NLA as I can see it, at least the outer springs.
So springs I think would be a good addition to the rare 924 parts.
I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too. |
Maybe Corentin can help you with the analysis of that to see what you need with the boost+RPM, he have put together a model for valve train analysis that might be possible to use.
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That would be very helpful and appreciated !
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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safe
Joined: 18 Mar 2017
Posts: 687
Location: Sweden
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| Posted: Fri Oct 17, 2025 10:26 pm Post subject: |
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A tangent to valve springs, if anyone know.
Why do we have a rotator (name??) under the exhaust valves?
Is it really needed and why?
I haven't seen that in other engines and they are NLA too.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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Coco_Lev
Joined: 04 May 2020
Posts: 104
Location: France
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| Posted: Fri Oct 17, 2025 11:04 pm Post subject: |
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| safe wrote: | A tangent to valve springs, if anyone know.
Why do we have a rotator (name??) under the exhaust valves?
Is it really needed and why?
I haven't seen that in other engines and they are NLA too. |
Rotocaps are used because they allow for better valve sealing. Thanks to the higher rotation freedom, they help to clean the valve seat faces when the valve rotates. Better sealing = better compression + better heat extraction to the seat. It was a common technology at that time.
They are mandatory in the sense that they compress the valve spring to the correct installed height. If you use standard lower spring seat, the installed height will no longer be correct, and the spring force will be too low.
You could perhaps machine a lower seat to the correct height, but you will still loose the primary function of the rotocap : enhance the valve rotation.
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Raize
Joined: 18 Sep 2013
Posts: 398
Location: Scotland
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| Posted: Sat Oct 18, 2025 5:12 am Post subject: |
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| safe wrote: | | I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too. |
What other components would you want to change for 7500? I know at least the solid, shimmed cam buckets are needed.
If you could get 7500 by just changing cylinder head components it would be a pretty decent "Stage 1" upgrade.
I guess the issue with the stock springs is variability, some might be good to 7500 and some might be valve floating at that speed. If these new springs are precision made and maybe even tested then it would be less of an issue. |
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Cedric
Joined: 27 Aug 2004
Posts: 2761
Location: Sweden
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| Posted: Sat Oct 18, 2025 5:47 am Post subject: |
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| Raize wrote: | | safe wrote: | | I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too. |
What other components would you want to change for 7500? I know at least the solid, shimmed cam buckets are needed.
If you could get 7500 by just changing cylinder head components it would be a pretty decent "Stage 1" upgrade.
I guess the issue with the stock springs is variability, some might be good to 7500 and some might be valve floating at that speed. If these new springs are precision made and maybe even tested then it would be less of an issue. |
The challenge is to actually make any significant power there, would need porting work, cam, intake and probably some exhaust work
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safe
Joined: 18 Mar 2017
Posts: 687
Location: Sweden
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| Posted: Sat Oct 18, 2025 6:09 am Post subject: |
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| Raize wrote: | | safe wrote: | | I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too. |
What other components would you want to change for 7500? I know at least the solid, shimmed cam buckets are needed.
If you could get 7500 by just changing cylinder head components it would be a pretty decent "Stage 1" upgrade.
I guess the issue with the stock springs is variability, some might be good to 7500 and some might be valve floating at that speed. If these new springs are precision made and maybe even tested then it would be less of an issue. |
I think that a lighter rotating assembly is needed and solid lifter buckets. If better springs ir needed, I dont know.
Mittelmotor sells a racing camshaft that specifies powerband betweenn 5500 -7500 rpm. They state that you need lighter piston and rods, but nothing about valve springs or lifters for that matter.
The old 911's always had a valve train capable of 7500-8000 despite a 6500 redline, basically the same springs from the 2.0 to the later 3.2.
But better springs and Im all in.
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/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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Coco_Lev
Joined: 04 May 2020
Posts: 104
Location: France
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| Posted: Sat Oct 18, 2025 6:22 am Post subject: |
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If you switch to solid buckets, you will save about 25grs, resulting in an extra 500 rpms potential.
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Raize
Joined: 18 Sep 2013
Posts: 398
Location: Scotland
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| Posted: Sat Oct 18, 2025 6:54 am Post subject: |
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| Cedric wrote: | | Raize wrote: | | safe wrote: | | I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too. |
What other components would you want to change for 7500? I know at least the solid, shimmed cam buckets are needed.
If you could get 7500 by just changing cylinder head components it would be a pretty decent "Stage 1" upgrade.
I guess the issue with the stock springs is variability, some might be good to 7500 and some might be valve floating at that speed. If these new springs are precision made and maybe even tested then it would be less of an issue. |
The challenge is to actually make any significant power there, would need porting work, cam, intake and probably some exhaust work |
I never really understood that in the context of forced induction because surely the turbo/super just forces the CFM in there and the volumetric inefficiency would just be seen as an (irrelevant for combustion really) pressure spike… |
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safe
Joined: 18 Mar 2017
Posts: 687
Location: Sweden
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| Posted: Sat Oct 18, 2025 7:24 am Post subject: |
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| Raize wrote: | | Cedric wrote: | | Raize wrote: | | safe wrote: | | I'm looking to get some better springs that can rev to 7500+ with boost. But I think that the stock springs might actually be good for that already. But it depends on the cam too. |
What other components would you want to change for 7500? I know at least the solid, shimmed cam buckets are needed.
If you could get 7500 by just changing cylinder head components it would be a pretty decent "Stage 1" upgrade.
I guess the issue with the stock springs is variability, some might be good to 7500 and some might be valve floating at that speed. If these new springs are precision made and maybe even tested then it would be less of an issue. |
The challenge is to actually make any significant power there, would need porting work, cam, intake and probably some exhaust work |
I never really understood that in the context of forced induction because surely the turbo/super just forces the CFM in there and the volumetric inefficiency would just be seen as an (irrelevant for combustion really) pressure spike… |
Yes, with a turbo you can pile on extra boost up high to compensate the ineffecency in the head.
I step up the boost at 5000, reaches peak at 5600ish and rides out so I got peak horse power at 6600, which was my revlimiter, I have it set to 67 or 68 now.
_________________
/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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