It can be relative and i can also not be relative. There is more than one way a spring can wear down. Load loss as a whole, the changes will be relative. There is also fatigue where there will start to form micro cracks and that will effect the spring rate, so your open pressures will drop more than closed pressures.

In short, there is no rule of thumb.

 

Generally, valve springs will lose open pressure values more quickly than closed pressures. But not in any calculated amount, per your example. Within a set of valve springs, some springs may lose 20% of open pressure and 10% of closed pressure, then another spring in the same set (and application) may lose 25% open pressure and 5% of closed pressure. And another spring within this set may not lose any pressure, open or closed values.

 

How does a spring lose anything but rate unless maybe a progressive spring?? Does one end of the spring wear out before the other?

 

If in doubt change it Out... if a spring is purchased with X amount of open & seat pressure with time and wear nets what loss on X or" the original Open amount of X and the Need of the cam lobe Wanting X amount of Seat and open pressure.

You answered your own question The lobe Wants What and what's deemed acceptable.

 

Just turn them upside down

 

When a coil spring wears out and begins to lose pressure (spring rate) this wear does not affect one end of the spring, or the other, but rather the total spring. It would be highly unusual for the spring to lose pressure in a linear fashion. A typical valve spring might lose 12% of it's open pressure and 7% of it's closed pressure, for example. And a set of valve springs in a subject engine will not lose the same amount of spring pressure (spring rate) as the spring ages and wears out. Some of the valve springs may lose 12 to 15% of open pressure and 7 to 9% of closed pressure. Valve springs will usually have a greater loss in pressure (spring rate), percentage wise, at the valve open setting than at the valve closed setting as they are subjected to normal wear and life-expectancy.

 

'.... Valve springs will usually have a greater loss in pressure (spring rate), percentage wise, at the valve open setting than at the valve closed setting'

Thank you

 

My very limited experience with this topic:

Valve Springs -

I'm doing a little refresher on the A-460 headed 565 Ford. Going to do some dyno time this winter to figure out a few things. The 565 has been together since 2011. First couple of years I would back off the rockers over the winter ( non-river season) Then for a few years I would just spin it...

www.yellowbullet.com

The heads went together with a set of PSI Super Clean Silicone springs ( dual spring) I think it's the spring Crower sold as PN: 68755.

When they were assembled in 2011 they went together at 300 on the seat at 2.115" & 725 @ 1.344"

Yesterday they were checked at 295 and 715. ( The weakest of them)

***

That's 1.7% loss on the seat and 1.4% over the nose.

 

I know an engine builder who kept an roller cam spring compressed in a vise for ten years. No change in pressure. One more proof that heat kills them if anything?

 

Just my opinion but I would probably listen to the guy in the thread that works/worked for a spring manufacturer.

 

I'm under the impression that heat kills springs far more than the action of compressing and expanding does.

As Scott stated earlier:
" The one way a spring might lose it's rate in a a progressive fashion would be from heat where one end of the spring sees more heat than the other which, in a running engine, may be very common. This is why I'm not willing to go out on a limb and say positively that springs always wear in a linear fashion."

Take a paper clip, or a piece of clothes hanger, or a fork and start flexing it. The area that gets the heat fatigues, not the entire piece. The end of the spring that gets the most heat would more than likely be the side that loses psi. ( all else being equal)

 

Remember, the OP's original post asked the question "As valve springs 'wear' is the loss the same for both seat and open and pressure"

The correct answer to his inquiry would be a selection (or combination) of the following:

No!
Never!
Not as result of our testing/examination
Very, very unusual
Possibly, in very few instances, (according to legend/beer infused bench racing discussion)

Take your pick . . . . . . .

 

turbobuick6 poster #2 and maybe others too IDK

 

Turbobuick


Ah..... treed

 

sounds reasonable to me too

 

If it helped performance or reliability, would Pro Stock engine builders use spring oilers?

 

Pretty sure they do.

 

I googled 'offshore spring oiler valve cover', because I know they run them, and found all sorts of LS stuff, but I'm probably behind the times...

 

PS absolutely runs spring oilers
still destroy springs but less rapidly...lol.
with say 1.200 ish lift at 11,000 rpm, thats a lot of exciting the spring and a lot of movement
we have a nice computer spring dyno i run every spring on.
I have seen springs that did not follow the original trace in a parallel line, but steadily dropped away the closer it got to bind.
I dont measure all the springs when we take them off, but i will do so for awhile to see if it was unique to this spring, or if it was an anomaly. I suspect i know the results, but well see

 

So much sandbagging in this statement Bob LMAO.

Were you ever able to find retainers for the 1.500" duals?

 

ok. just ran some manley 221422 duals we had on a 9600 rpm LS superstocker.
these were pretty low run, so im disappointed in the amount of loss but it does explain why it seemed to not run as well after time
lost 60 ish on the seat from 280 ish to 220 ish, they varied
lost 25 over the nose from 850 to 825. Some lost a little more some lost a little less, but that was roughly the average
what does that mean? idk for sure, but i found it interesting it went that direction
might be the initial exciting of the spring is bouncing a few coils off each other creating micro hot spots so that area of the spring lost more? would probably be my guess.
the 500 if you didnt give it enough clearance to bind would hit hard enough to micro weld in a small location and it would shatter. I always blamed that on the initial shock/exciting of the spring causing it to surge.

 

There is an excellent article on automotive valve springs in the latest issue of ENGINE PROFESSIONAL magazine, written by Fernando Curello. The article discusses several aspects of valve springs, some of which are associated with the factors that we are discussing in this thread. I recommend this article to anyone who is using high performance valve springs (just about all of us, eh?). Professor Curello is working on a follow-up article which will discuss the dynamics involved in the automotive valvetrain. This article will probably be presented in the third or fourth quarter issues of this publication.