Valve spring rates

Discussion in 'Workshop Forum' started by rjplenter, Oct 27, 2015.

  1. Hey gang,

    Can anyone confirm my calculations regarding standard valve spring rates?

    By my calculations the outer spring is 135lb/in and the inner is 80lb/in.

    I have found conical valve springs of the correct dimensions and rated at 215lbs/in and I'm seriously considering these for the new engine build.


  2. Sandgroper

    Sandgroper True Classic

    Down Under
    So just to get it clear you want to go from dual valve springs to a single

    Aren't the benifits of dual springs to limit harmonics (limit spring surge) its kinda the reason that Lampredi put them in to allow for a free reving stable valve train me thinks.

    Is it that the single valve spring setup is simpler and lighter that you are chasing?

    IMHO if you are looking to lighten the valve train are you looking at Ti buckets/ keepers and ground lash caps? I found this a more successful route in the XU9 Peugeot engine to get rid of some valve bounce.

    Unless you mean the new fandangled Dual Conical Valve Springs, I had my head around the progressive 'beehive' type spring which is allegedly very effecient at dampening itself, these conical ones I have no idea.

    Going to single seems like a backward step, I'd like to understand if you think it is not.

    Poor image but I think you can make it out

    Last edited: Oct 28, 2015
  3. The illustration above shows individual spring rates

    I can't recall what the combined rates end up being at the prescribed lift, but I do know that installed seat pressure should be 114lbs.

    Keep in mind that more pressure is not better, and we've proven that 114lbs of seat pressure works just fine to control valves to 10,000 RPM.

    A lot of parasitic loss happens in the valve train, between valve spring tension and cam lobe friction.

  4. fiatfactory

    fiatfactory Steve Cecchele

    Western Australia
    Matt's correct, the important values are seated and "over the nose' pressures when it comes to valve springs...and of course coil clearance to prevent bind up at full lift.

    Will conical springs even fit under the tappet buckets without interference?

  5. Sandgroper

    Sandgroper True Classic

    Down Under

    Is that wrong to list the individual rate for each spring? I don't understand why it would be.:confuse2:

    The way I read that image of the factory manual (in Lbs) if its hard to see (nominal)

    85+33=118 (installed heigt)

    141+64=205 (compressed height)

    Still interested in the benifits of a single over the dual spring setup
  6. Rupunzell

    Rupunzell Bernice Loui

    Object of this game is to keep just enough pressure on the valve seat with the valve face to keep a reliable seal without bouncing the valve against the valve seat above the absolute max engine RPM. Any more results in power loss in the cam drive system and numerous other areas where friction increased with loading (bearings and such).

    Concept behind double springs, conical shaped springs, Beehive shaped springs, friction spring dampers and such are to reduce or control the self resonant frequency of the springs-valve mass, opening-closing forces.

    Keep in mind when the bomb goes off inside the combustion chamber-cylinder that is going to be a LOT of force driving that valve hard against the valve seat to aid in sealing.

    Each time the cam lobe begins contact with the valve follower is about the same as a hammer beginning to tap on the valve follower. This pounding action is some what similar to hitting a bell with numerous self-resonate frequencies and wave nodes.

    Imagine trying to drive a vehicle with springs in the suspension but no dampers? Tires, driver and .... are NOT going to be happy at all.

    The idea of increasing spring rate is to increase self resonate frequencies to prevent the valves and all related from bouncing. This sort of works, but there are other ways that help reduce this.

    Increasing the spring rate of he suspension to where the whole chassis-suspension-driver and all chatters with very little suspension movement. The vehicle essentially hops and jumps over bumps rather than following the road contours and bumps in a controlled manner (tires have a spring rate that is significant once the chassis spring rates get obscene, Tires also have hysteresis and damping issues added to what is happening).

    Lowering the overall mass of the moving valve train parts will shift this self resonant frequency up. This is why so many current race motors use titanium valves-valve locks-spring retainers, small diameter valve stems (helps to reduce intake port obstructions too) and such.

    Using two different spring rates results in two different self resonant frequencies. As these two different self resonant frequencies work against each other, they loose energy fighting each other. This effectively helps to damp or control the system and goes a way to prevent the valve from bouncing against the valve seat.

    The ramp rates on the cam lobes also makes a BIG difference in valve behavior. This was the very problem Keith Duckworth had to deal with when the first Cosworth V8 race motor was designed. Lots of messy math later, they had to go by trial and error along with all that messy math to get the cam ramp rates correct for reliable valve train operation at high RPM.

    Cams also have a quiet side or as the valve is closing against the spring, this rate of change can also be controlled by the lobe of the cam. Good performance cams have non-symetrical lobe shapes to account for rate of change for the valve opening and rate of change for the valve as it is closing.

    IMO, use the lowest possible valve spring rates that causes no problems at some margin beyond the max engine RPM. Double valve springs are proven to do fine in the Lampredi SOHC engine. Even stock as delivered, the valve train has little problems above 7,500 RPM constant if all parts involved are in good condition.

    I'm not sure how effective conical valve springs might be, There is hard science behind the idea, it is the real world results that matter. This needs to be balanced against real world experience of many who have built lots of performanized motors that live fine above 8,000 PRM in endurance race duty.

    If it works, why fix it?

    BTW, when Renault introduced the pneumatic driven valve trains, more than a few believe the French were off their croissants and butter. Except, that idea worked and worked really well. This was part of what ushered in the 20,000 RPM Formula One engine era due to the ability to control valve train self resonant frequencies, valve operating time and all that related stuff.

  7. I am considering these for a few reasons

    Power is made in the head and parasitic losses can be high in the valve train.

    The new engine has larger valves, which are heavier.
    It has a more aggressive camshaft.
    I rev my Fiat engines like there is no tomorrow. :)

    I am reducing some of the weight in the valve mechanism by using lash caps. Based on preliminary measurements this will partly offset the weight of the bigger valves and reduce each mechanism by 1 gram compared to standard parts. That's definitely a good start given the cam will be moving them further with higher acceleration and deceleration rates.

    Double valves were introduced to reduce harmonics and it has worked very well for a long time. Now there are beehive springs and conical springs. The latest conical springs are shaped like a cone (with the top cut off) and the wire diameter changes through the length of the spring and so there is less harmonic built in. A conical spring has a smaller diameter at the top which allows for a smaller retainer which reduces weight.

    Nothing is made specifically for our engines, but there are springs out there that may work.

    My research continues...

    Thanks to the wise sages for their input and questions.


  8. fiatfactory

    fiatfactory Steve Cecchele

    Western Australia
    The twin cam engines all use bigger valves....even the 130 V6 with 44/40 valve sizes uses the same spring...that's what I've used for years with no issues, I just drop as much weight off the valve assembly as possible.

    1mm of shim thickness is a few grams... surely your saving that with the lash caps?

    I have some weight comparisons of shims / buckets etc somewhere...I'll dig them out.

    I'm using shim-less buckets at about 48 grams a piece...the standard bucket and a 4mm shim is about 81 grams...only thing is the initial setup with lash caps and then having to remove the cambox to do a tappet clearance adjustment...but the weight savings are pretty significant.


    I also have some alloy retainers, but not sure if I want to trust them on my race engine build... Ti ones are available, but expensive (but light) ...there's Ti and there's Ti too...certified alloys...DiFulvio in Italy sells ones that I would trust ( ) They seem to be the ones all the 12k rpm engines are wearing without failures. Ti retainers are around for other engines, so something might be compatible...I've been meaning to look at some VW golf 8v ones but haven't had the time yet.

    Last edited: Oct 29, 2015
  9. Yep, I'd have to look it up to be sure, but I think the big valves with lash caps are about 8 grams heavier, and the lash caps will mean about 9 gram lighter shims.

    Just like adjusting an Alfa engine. Tedious, but worth it in this case.

    Check these out:

    That's just a sample, there are plenty of options.


  10. Rod Midkiff

    Rod Midkiff True Classic

    Eugene, OR
    strange thought

    I was poking around y-tube a few months ago and came across something interesting. A different type of valve system. instead of a valve that open's and closes.. The cam has holes drilled in it. and it rotates in a cylinder. This open's and closes the passage way. And this way get's rid of the back and forth bouncing of the valve train.

    I do not know if anyone is actually doing anything with this thought. But if they are this seams like a perfect mod to do to the already high revving motor the X is famous for.
  11. kmead

    kmead Old enough to know better

  12. Sandgroper

    Sandgroper True Classic

    Down Under
    Thanks Bernice

    I was aware of the French F1 engine as I followed the 1st Turbo era closely, a pity they have dropped the ball lately, but I never really studied the pneumatic valve


    Careful the F1 link is full of engine pron, I love that inlet tract


    Gotcha, then you are in the experimental zone and thinking available spring sets may be overwhelmed.

    Thought bubble allert!

    A long shot but if you are at the design stage then don't be surprised if this parts cross refernce comes close. Having had both of these in my hands durning a build they looked similar to a Fiat in size but I never measured them. The springs for a larger heaver Pug valve that can fit in the 1.9 Ltr chamber may fit the buckets you have.

    I have a few spare heads sitting back in the shed I could measure but until I get back have you thought about the XU9JAZ setup, this is the system you are looking at. They have a very wide selection of lash caps and one of the boffins in that world had worked out that some Datsun aftermarket springs work inside the buckets. You never know!



    Did the US ever see the Peugoat 405 205 eight/sixteen valvers? There was a lot of shiny stuff available when I built the last Pug eight valver nearly a decade ago, I know the French like to stick with a component design once they have arrived at it so its probably still freely available.

    You are both correct in that adjusting the lash is changing the belt/cam off when you go this way, PITA but once it settles in - rock solid. Over the last 7 years the gap hasn't moved with none of the failures in any of the Pug race engines that is sometimes seen in the Lotus where the lash cap goes walkies.
  13. fiatfactory

    fiatfactory Steve Cecchele

    Western Australia

    are those lash caps for 8mm valve stems?

    What diameter is the Pewgoat bucket?


    I believe it's an early 8v golf engine I'm looking for... many many moons ago I did a top overhaul on a friends golf and was amazed at the similarities in the valve actuation design, and I have a feeling the retainer for the 8v 8mm stem style will do the job...just need to chase up the stock parts with my head-man Jerry and see if they are compatible when measured side by side.

  14. 8mm stems

    It appears the XU9JAZ engine did indeed have 8mm stems.
  15. Sandgroper

    Sandgroper True Classic

    Down Under
    Good questions

    Probably 8mm but let me measure, I'm a few weeks away from being back so after letting go of the Dropbox acct ( did you see how much they want now? OMG) I don't have too much Pewgoat data at hand. Its back in the shed.

    I will rip them both out ( Fiat and Pug ) for pickies and measure the valve trains if you like.

    Dia? Weight? Height ? of the buckets

    Spring Dia / Height LBS

    anything else?

    The range of shims I can remember is very extensive as the system the French used was over their 8 & 16 valvers in a number of engines.

    I have a truck load of Pug stuff and as I never had a problem with the SOHC didn't get serious about swapping bits.

    Rob's probably correct though the valves looked similar but I think the stem heights will be way off. We are really only worried about the rest of the valve train I guess.

    Let me get back to you.
  16. fiatfactory

    fiatfactory Steve Cecchele

    Western Australia

    lash caps are of interest, as I'd like to find a reliable OE source in a good adjustment range for something that suits the Fiat SOHC when fitted with the shim-less buckets... in the past I think I settled on Alfa nord shims (cos I had a selection available) but they were for 9mm stems and didn't 'click' onto the valve ends as I would have liked them to, but they worked.

    The buckets...well just a quick comparison tosee if they suit the SOHC Fiat... again it would be nice to have an OE source to interchange.

    The buckets I got from Croatia I'm not too sure about... they aren't like the Pittatore ones I have used in the past in that the working surface doesn't appear to be hardened in any way, whereas the Pittatore items I used in the past were definitely nitrided items, and then reground to size..i.e the cylindrical part was shiney and the working surface and underside was that dull grey nitrided colour...the ones available from sources in Italy (like DiFulvio) are definitely nitrided...but pretty expensive at around 240 euro a set (compared to around 90 euro from Croatia un-nitrided)

    I kind of like the idea of two nitrided surfaces working together (OE shims are nitrided) and I'm a little worried about wiping out my expensive Pittatore 12.2mm lift nitrided steel cam lobes... so I'm going to try these croatian ones out in my 1500 mule engine, which has a lower lift (10.6mm) but same duration (42/82) cam, again a Pittatore Nitrided steel, but I've got a few of these to spare ...I only have the two with 12.2 intake lift ...which I bought secondhand from forum members and both had damaged exhaust lobes which I've had re ground to a lower lift,so I'm not sure about the hardness of the exhaust lobes anyway, as these were done by Tighe cams.

  17. Sandgroper

    Sandgroper True Classic

    Down Under

    You have a PM

    Best Regards
  18. Steve, if you want 40gm shimless buckets

    Part number CF-37/3.3

    They look to be the real business and retail for 18.71USD each. That's cheaper than I would pay to have standard Fiat parts machined and nitrided.



    Here's their sales pitch:
    Supertech buckets are designed using the latest CATIA CAD software along with Finite Element Analysis (FEA) to ensure the utmost performance and durability under the most demanding racing conditions. Utilizing these methods to analyze the stresses associated with the off centered application of loads enables us to maximize the strength of our buckets while reducing weight. Supertech ensures that each and every part is manufactured using only the highest quality materials, strict tolerances, and high quality coatings. The end result is an undeniable improvement in durability and performance that cannot be compared in any sense with less expensive, extruded or factory supplied lifters. So regardless of your racing applications… whether it is road racing, drag racing or endurance racing Supertech buckets are engineered to outperform the competition to a degree that can only be found in Formula 1.

    •Aerospace certified Chrome-Molybdenum-Vanadium alloy from Austria. This is a much stronger material than the alloys used in OEM extruded lifters.
    •Completely CNC machined from heat treated billet provides only the necessary and calculated thickness of the walls with very special shapes, providing better rigidity with an important reduction in weight.
    •The lifters are fully Nitrided and polished to harden the surface to about 60Rc for low wear. Higher cam lifts and rpms will submit conventional lifters to be susceptible to increased wear.
    •Surface is carefully finished by grinding it to a much lower surface roughness for lower friction with the cams and cylinder head bore, providing improved durability.
    •Overall improvement in durability
    Last edited: Nov 3, 2015
  19. fiatfactory

    fiatfactory Steve Cecchele

    Western Australia
    They look OK...

    I'm not at home right now, so don't have any measurements...still gonna be close to $200au for a set... but I'm more concerned with quality than cost... good cams are to expensive to take chances on.

    For your 1600 I think it's worthwhile going to go down this route, you've come this far, why cut corners.

  20. I hear what you're saying Steve

    But, how can we ever know if a part is good enough? Not being argumentative, but just wondering how do we judge that?

    Price can be a measure, i.e. cheaper is not always better, but if something is produced in large numbers rather than being a specialty item cost can be reduced and passed on to the consumer. DiFulvio's version is 70% more expensive, but I wonder how many they sell.

    I think ARP fasteners are reasonably priced for what you get. In that case they make and sell tons of quality fasteners and so the business is profitable.

    These buckets are the correct diameter at 37mm diameter and 1-2mm shorter than ours, I didn't realise the length of our buckets varied so much. I'm no metallurgist so no idea if Chrome-Molybdenum-Vanadium is appropriate for buckets but it is a pretty hard steel alloy.

    I'm happy to stick with Plan A, lash caps on the valve stems and thin shims on traditional buckets. They'll be easier to set up. But you know me, I'm looking at ways to reduce parasitic losses. :)



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