Race valve springs - steel or iron cams?

[promotor]

I am just looking for a couple of answers regarding race valve springs and cams.

Do race valve spring working pressures mean that billet cams are needed?

I'm looking to have some standard Lotus cams reground to maybe .420" spec and wonder if they are up to the task without breaking? I know that there is the long bolt mod for Iron cams - when is the long bolt method needed when using iron cams? Is it rev dependent or valve spring/cam load dependent?

Or is it just the case that I will need to fit billet cams? I know Billet cams also means I'll need steel followers if I have to go that route!

Any help / theorizing etc would be great!

[rgh0]

You should not go over 220 lb nose load with race springs. This load will work with both iron and steel cams up to over 9000 rpm. With an iron cam you need to drill and tap the end of the cams and fit the longer bolt, so the nose of the cam does not break off under the higher loads. The bolt runs down past the first bearing and needs to be drilled for an oil passage to feed that first bearing. If you limited your revs and spring loads to normal road type levels you could probably get away without the long bolt mod with something like at QED 420 cam, I presume QED would have a recommendation around that.

You will generally need to use steel followers these days as that is what most people stock. I am sure you may be able to find iron ones if you look around hard enough. With a high lift cam depending on the rest of the setup you may need to use a thinner steel follower in any case to get adequate shim thickness.

An iron cam is preferred with steel buckets from a wear perspective as the steel on steel can result in galling. If running steel on steel you need to try to get at least a 10 Rockwell C hardness difference between the cam and follower and use a phosphate or DLC coating on the followers to prevent galling on run in. plus lots of running in lube.

cheers
Rohan

[promotor]

I should have titled my thread "Rohan, can you please answer a question for me please?" as I knew you would be a likely respondee!!

Thanks for your response. The engine will be a balanced 3020e bottom end and forged pistons. How do I work out spring pressures without a spring gauge? I have a tool that will allow me to accurately measure the compressed valve spring height - are there some sums I can use to work out expected poundage at full spring compression?

[rgh0]

What springs are you using? I have attached a spread sheet with the load versus spring height for most of the currently available standard and high lift springs that I have measured. You can buy a simple spring load gauge for around $80 (or use an old set of bathroom scales with a couple of plates so you don't distort or break the case). You just need a press or vice to compress the spring with the gauge and measure its height while you read the gauge.

cheers
Rohan

spring load ranges.xls

(28 KiB) Downloaded 510 times

[promotor]

Rohan,
Thanks for that - very useful!

I will be measuring my spring lengths tomorrow and I will get back with a few more details.

I can say that they are QED race valve springs - they have the orange/red paint on them.

I did think about using a set of bathroom scales to measure the springs but got confused with the pounds per square inch - does that mean the springs needs to be placed on a plate 1" square to get an accurate reading? Or is it that I just need to measure the reading on the scales at various incremental valve spring length?

[rgh0]

The spring rate is measured in lbs per inch of compression. The spring load is measured in pounds at a particular free length. The key loads are a minimum of 60 lbs at the installed spring height with the valve closed and less than 220 pound at what ever is full lift for the cam you are using. You also need to be around 1.5mm or 60 thou of an inch from coil bind at full lift.

You can generally always achieve this load range without having to machine the sping pockets by the correct selection of springs, retainers and other component dimensions in the valve train

Compress the springs and measure the load as it is compressed from its free length up to its coil bind point. Do it assembled iwth the inner spring and with the retainer to keep the relationship between the inner and outer spring the same as in the engine. The length versus load I show in the spread sheet are the measured length of the outer spring itself versus the spring load of the assembly.

regards
Rohan

[promotor]

It's been a while since I did anything regarding this.

I have measured the springs that I believe to be QED race springs but was hoping whether someone may be able to confirm if they are or not? They look to have been covered in a red paint all over but this appears to have flaked off over time. The spring OD is smaller than others - 28mm as opposed to 31mm - and are 41mm free length. They came as a complete set of seats, springs, top hat shim type retainers, and very thin collets.

I have compared them with some another unknown spring set that came with bases and retainers - I think they came with some L1 cams I bought - again - if anyone can identify these that would be helpful! - the springs are 38mm free length - and taken a photo with the standard ones on the left, possible L1 (Q55??) springs in the middle, and the supposed QED race on the right :



I also assembled a standard retainer with standard cotters onto a standard valve, and then assembled the unknown retainer (from the spring in the middle of the three) onto a standard valve with standard cotters - the retainer sits approx 2-3mm higher than a standard retainer so it seems that these are for higher lift cams by way of giving more spring room. I'm not sure if these retainers should have standard collets or not? :


Standard retainer on the left, unknown (poss Q55/L1) on the right.



Collet from the race springs on the left, standard on the right


Race retainer on the left, and retainer on the right poss Q55/L1?

I would think it's hard to say for sure what the parts are but thought it was worth it to get a list of possibles (or definitive not possibles) and then I may see about measuring their spring strengths if I get chance.

[rgh0]

The Spring on the right is almost certainly the QED race spring. I am working from memory as I am currently moving house and don't have access to all my spring sets as its all packed up for the move so hard to positively identify the other components. I will dig through some photos I have and see if the other parts can be recognised.

If you are building a new motor I would be very cautious about using second hand valve train components of unknown / uncertain previous history. Dropping a valve makes a big mess of an expensive motor very quickly!! been there done that.

cheers
Rohan

[rgh0]

Cant find my photos - my computer filing system is in a mess I really do need to clean it up -- maybe I did and I deleted the photos !!!!!

I do however have all my detailed spring and retainer measurements available.

The middle spring may be a Q55 or a Dave Bean Race spring. If you can give me some dimensions - OD of spring, spring wire diameter and free length and number of working coils then I can be more positive.

With the retainer give me each diameter and length of the various steps in size along the retainer.

cheers
Rohan

[avro]

Hi Al
The spring on the right is as Rohan thought the race spring that QED supply and they come painted orange. (manufactured by Iskenderian) . It has a smaller OD and ID and will not fit the standard spring retainer. QED offer it as a spring package and its supplied with suitable retainers, smaller diameter platforms and smaller OD colletts. Looking at your pictures you may have the smaller colletts. The retainer for these springs only allow the use of the smaller diameter top hat shims.
The middle spring in your set is definately not the Q55. These are manufactured with a finer wire both on the outer and inner spring and have a much longer free length ( 1.750" compared with a standard spring free length of 1.400") . Looking at your photo, its slightly longer length and the fact it came with an old set of L1 cams leads me to believe that its most likely to be a Cosworth spring. These need to be used with a Cosworth retainer, otherwise when used with a high lift cam the spring will become coil bound. The Cosworth retainer is machined so the spring sits higher up the retainer in relation to the valve tip. (Appox 60 thou) so allowing an increase of cam lift to the same amount without the need to machine spring platforms.( A machining operation thats totally unnecessary these days with the wide variety of parts now available.) This spring and retainer is still available from Cosworths but can as I recall only be used with lifts up to .430 thou when installed at the recommended fitted length of 1.300".

Kind regards

Nick Stagg

[promotor]

Again, thanks for the replies!

Rohan, having records and files on computer almost always means needing a index system to go with the files otherwise for me things get messy! Are you still in the middle of your house move? Not asking for selfish reasons just so that you can help with my problem!

I have taken a few measurements of the springs and here is what I get :
Free length 38mm
Wire thickness 4mm
OD spring 31mm
4.75 total coil turns (not sure what "working coils" are defined as?)
19mm coil bind.
The retainers are the same dimensions as standard retainers EXCEPT for the fact they allow standard collets to sit further down inside.

I had a look at your excel spreadsheet on spring load ranges and the Q55 figures were surprising - 115lbs maximum load at 19mm installed height? Is that a mistake? or are they made of an unusual material as they are way short of the standard spring figures!!

Nick - hope you are well? And thank you for taking the time to reply!
For the benefit of both you and Rohan (as well as my self of course!!) I have fitted the mystery springs with a fitted length of 1.3" and found that I would have 0.570" total lift before being coil bound. Having applied the scientific test of compressing the installed spring assembly by hand I surmise that these springs are fairly stiff!
I'm currently looking into getting a valve spring test gauge to do a proper test though as this has got me interested!

I'm only planning on using upto 0.420" cam lift so these seem to be adequate unless short duration high lift cams require a different spring action to those found to be suitable with longer duration cams i.e L1 etc?

[rgh0]

Still packing stuff up for the move. Relocate in October.

The springs don't match anything I have measured to date assuming the 4mm wire diameter is accurate i.e. 4.0mm diameter. So probably Cosworth springs as stated.

Spring rate free length and stresses look OK and should be good for a 0.42 lift cam if the rest of assembly matches up OK which it should

Normally the last coil of the spring at each end does not "work" as it is flattened and ground flat. Thus a spring with 4.75 total coils will have around 2.75 working coils.

A short duration high lift cam versus longer duration high lift cam does not really change the spring requirements.

I have seen a few people have problems with retainers pulling through the collets in race engines so you need to be careful you have a proper match and proven design of retainer and collets and not try to mix and match without care.

cheers
Rohan

[promotor]

Thanks for the response Rohan and good luck with the move!

I have new valves and collets so they should be good for not pulling through.
I think the assembly has enough room for a modified camshaft with the correct base circle, and using the thinner followers.

I believe the head is good for 150bhp so with 420 cams and 7000rpm I should be there or there-abouts. Looking forward to getting it together once I have sorted some custom pistons out.

Cheers once again.

[SJ Lambert]

I've got a set of Cosworth springs that haven't done much work - I'll test them some time (not soon) and report back.

Are original spec Cosworth springs still available anywhere?

[SJ Lambert]

Looks like I'm OK in avoiding coil bind, but am falling foul of the 220 pounds over the nose rule (haven't used a calibration spring in the tester, but installed height measures 80 lbs like they're supposed to).