Do you think I can get by with the old springs?

Since I was playing with springs today and recalibrated my tester I decided to show something.

I pulled 7 valve springs out of my bucket of springs removed from heads I rebuild.

Here they are lined up. The spring on the right end with the retainer is a new spring from Andover.



Here are the results at the recommended installed height of 1.280















That last and lowest spring was the fairly tall spring next to the new spring.

Here is the new stock spring.

Back in the 1930s, which was a fair while ago technically speaking, Terrys recommended changing valve springs after every 2 race meetings.

There is a reason why manx norton valve springs can be changed using a big pair of tongs, between races if necessary,
no other dismantling necessary.

I miss those S&W valve springs, which were said to be good for life.
I assume that was my life, not theirs.
1970s Commando era, but alas made no more.

Rohan said:

Back in the 1930s, which was a fair while ago technically speaking, Terrys recommended changing valve springs after every 2 race meetings.

There is a reason why manx norton valve springs can be changed using a big pair of tongs, between races if necessary,
no other dismantling necessary.

I miss those S&W valve springs, which were said to be good for life.
I assume that was my life, not theirs.
1970s Commando era, but alas made no more.

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Sure they are, they are now called R&D spring.

http://rdvalvespring.com/

Would be interesting to know the history of the used springs i.e. mileage, type of use etc. I assume the tests are in the same order as the lineup? Notable that the best old springset looks to be the shortest. Do they elongate as they lose tension?

well that tells a story Jim, if you dont know the history of your cylinder head (springs) install new ones at first opportunity.
thanks for posting.

Danno said:

Would be interesting to know the history of the used springs i.e. mileage, type of use etc. I assume the tests are in the same order as the lineup? Notable that the best old springset looks to be the shortest. Do they elongate as they lose tension?

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I have found it is really hard to tell if a spring has any life left by looking at it or measuring it's length. The lineup is not necessarily the order of the tests. I really only kept track of the one very low pressure spring.

I don't have any history on the valve springs I measured. They are just a random sample from my bucket of springs that came from customers heads. I normally advise installing new springs when I do a rebuild but sometimes I will test them and maybe grab some from the bucket to put a usable set together for economy jobs.

Norton springs have a pretty tough life with the heat involved. I have noticed that new springs will loose about 10 lbs pressure in the first 100 miles or so and then after that they will very slowly loose pressure.

The bigger the cam and the hotter they run the faster they loose pressure. The Norton service manual says they should be replaced anytime the engine is de-coked -however often that is ???

Some of the newer high tech springs definitely hold their pressure longer -if they are not used in an extreme application. Jim

Interesting test Jim, thanks for posting.
It makes me consider replacement of the 40 years old valve springs in my commando. :shock:

i once spoke at length with Dave Degans ( Dresda Autos ) and he claims after extensive testing 55 pounds spring pressure was best for Triumph twin race motors
higher rate springs just added resistance to the valve train and actually decreased performance

i guess the Spring rates increase on road engines to ensure spring longevity as frequent changes are non viable

So, as long as a spring will keep the valve mechanism following the cam profile and close the valve on time up to the RPM the engine is actually run at, then isn't the weakest spring going to be easiest on the valve train? Back in the '70s Bill Bell, of Honda XL350 fame, recommended good springs but by far not the heaviest available. He said that the heavier springs wore things out faster.
Dan.

motorson said:

So, as long as a spring will keep the valve mechanism following the cam profile and close the valve on time up to the RPM the engine is actually run at, then isn't the weakest spring going to be easiest on the valve train? Back in the '70s Bill Bell, of Honda XL350 fame, recommended good springs but by far not the heaviest available. He said that the heavier springs wore things out faster.
Dan.

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If the spring is heavy enough to keep the vlavetrain all in contact with the cam then it will give the longest cam life. If the spring is not strong enough then you get separation of the parts which causes the lifter to crash back down on the cam. This will "wear out" a cam faster than a spring that is a little too heavy.

Valve train separation from weak springs is what causes the classic wear line down the center of a Norton lifter.

I would venture to say that more Norton cam failures were due to too light a spring than from a spring that was too heavy.
If you look at the classic failing Norton cam before the lobe is completely gone you will find the wear starts on the backside of the lobe -just past peak lift. This is where the lifter crashes back to the camshaft and breaks through the hardening first.

Here is a cam that was just starting to fail. It is graphed along with a good cam lobe. You can see where the wear is the greatest. In a short time this lobe would have been flat.



It takes a minimum of 75 lbs of seat pressure with the stock spring to keep the valve train from separating with a stock cam up to 6000 rpm.

With aftermarket springs with a higher spring rate it is often possible to run less pressure on the seat and still avoid valve train separation. Jim

I know that until the advent of pneumatic valve actuation, the springs were the weak part of any high-performance engine, so despite new alloys, heat treating and other metallurgical advances, springs have not kept up with other developments that yield higher and higher power levels. I think the springs in WSBK race motors are changed out after every event. Probably the same deal in Moto 2, where everyone races a spec Honda 600 engine.

Danno said:

I know that until the advent of pneumatic valve actuation, the springs were the weak part of any high-performance engine, so despite new alloys, heat treating and other metallurgical advances, springs have not kept up with other developments that yield higher and higher power levels. I think the springs in WSBK race motors are changed out after every event. Probably the same deal in Moto 2, where everyone races a spec Honda 600 engine.

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Yep, spring life is rather short when your using them for all they're worth. [ie- stock springs on a combat cam] Jim

I have recently sent comnoz two different head/barrel studs to twist apart to see if cryo tempering helps and www has plentiful reports of *deep* freeze helping valve springs so hope comnoz can test this for possible hi rpm and life extension. Here is a quote from one freezer to ponder...

Cryogenically treating your valve springs can increase spring durability 50% to 800%. Spring pressure may also increase 1% to 2%.

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I design springs all the time. What usually causes this is a cheaply manufactured spring that has not been set to solid. So, Jim, can you measure the free length and then crunch the spring solid. Probably won't have the same free length after.

baldy said:

I design springs all the time. What usually causes this is a cheaply manufactured spring that has not been set to solid. So, Jim, can you measure the free length and then crunch the spring solid. Probably won't have the same free length after.

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I tried 3 new springs. I just installed my last set of new Kibblewhite stock replacement springs so I didn't have any to test.

The new Andover Norton spring was 1.663 fresh out of the package- after 30 seconds at coil bind it was 1.656 for a loss of .007

The new Kibblewhite race spring was 1.932 " " " 1.918 " .014

The new conical spring was 1.761 " " " 1.753 " ..008


The used 90 lb spring was 1.601 and stayed at 1.601 Jim

comnoz said:

baldy said:

I design springs all the time. What usually causes this is a cheaply manufactured spring that has not been set to solid. So, Jim, can you measure the free length and then crunch the spring solid. Probably won't have the same free length after.

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I tried 3 new springs. I just installed my last set of new Kibblewhite stock replacement springs so I didn't have any to test.

The new Andover Norton spring was 1.663 fresh out of the package- after 30 seconds at coil bind it was 1.656 for a loss of .007

The new Kibblewhite race spring was 1.932 " " " 1.918 " .014

The new conical spring was 1.761 " " " 1.753 " ..008


The used 90 lb spring was 1.601 and stayed at 1.601 Jim

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That last one is the sort of part they cherry-pick to build a "stock" motor that performs better than actual stock motors made from randomly picked parts. An accident of above-average quality.

Jim said:

Yep, spring life is rather short when your using them for all they're worth. [ie- stock springs on a combat cam]

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I felt that jab, Jim. You have a mind like a steel trap! So - - what springs can I use on a combat cam that will allow me to use the same valves I have now? (Stock Black Diamonds) I like to run it hard fairly often but almost never over 7000 rpm and never on purpose.
Dan.

motorson said:

Jim said:

Yep, spring life is rather short when your using them for all they're worth. [ie- stock springs on a combat cam]

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I felt that jab, Jim. You have a mind like a steel trap! So - - what springs can I use on a combat cam that will allow me to use the same valves I have now? (Stock Black Diamonds) I like to run it hard fairly often but almost never over 7000 rpm and never on purpose.
Dan.

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Dan, I wasn't thinking of you particularly -sorry. But my new conical springs would work great. jim

I wonder at what rpm seat pressure becomes a problem with the clapped out springs?
If 100 lbs is ideal and the springs only shows 60, is power lost due to incomplete sealing throughout the range or is sealing still good up to some rpm where valves might start bouncing due to weak springs?
So where good springs might show good control to 7000 poor springs might still show good control to 5500 then lose it?

Glen

worntorn said:

I wonder at what rpm seat pressure becomes a problem with the clapped out springs?
If 100 lbs is ideal and the springs only shows 60, is power lost due to incomplete sealing throughout the range or is sealing still good up to some rpm where valves might start bouncing due to weak springs?
So where good springs might show good control to 7000 poor springs might still show good control to 5500 then lose it?

Glen

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The testing I did was with used springs that were 75 lbs at 1.280. They would run to 6000 before the rattle from separation became obvious with a stock cam.

They left a nice shiny line across the newly resurfaced lifters in just the minute or so that they were run.

I have no doubt the engine would continue to rev even with valvetrain separation. You might be able to hear the difference if you had another engine with good springs to compare it to.

My experience with springs that were not strong enough was the engine just seemed flat when it was revved. No big pops or obvious missfires.

I know the sound differences are very obvious on the spintron.

There have been a few cams that I tested that made me want my ear protectors because they made the valvetrain so noisy. Jim