Valve spring close to coil bind: good or bad for spring life?

[BradH]

I've searched a number of threads here and elsewhere about this question and am seeing knowledgeable people respond both yes and no: Does setting up a valve spring to run close to coil bind (e.g. .060") reduce the lifespan of the spring?

If I understand the comments correctly, the "no" side believes the reduction in surge from setting up the spring this way may actually improve the life of the spring.

And those on the "yes" side believe the spring being run under those conditions puts the spring into its highest stress point (short of actual coil bind) and increases the possibility of fatigue or breakage.

I don't know how much of the difference in perspective comes from experiences under dissimilar conditions. I.e., what's a "reasonable" life expectancy for a spring in a Pro Stock application vs what's required for the Daytona 24 Hour? Regardless, I'd like to know more about it. Thanks - Brad

[hoodeng]

The manufacturers recommendation for their spring is obviously the best way to go ,but i would have to say the majority of springs i install have bind height +.060" as the minimum installed height recommended.

In performance street application the prevalence of ovate springs is very common now in the product i service. I have a situation where i prefer to use one brand of spring if possible, the recommendation for the installed pressure and height for this spring gives about .120" bind clearance, i got back to the manufacturer and asked if i could go from 170lb seat pressure to 180lb and if i could run another .040" lift over the recommended .600" max lift, which used up .060" of the available clearance and they said no problem if the job is being measured out correctly, they added that the package label recommendation was on the higher side of clearance as they had found a number of people don't even measure what they are doing and just bolt stuff in because its new.
I had one shop take me to task over the fact i was writing all the springs installation specs on the backs of invoices, as far as they were concerned the parts were all new so why was i charging them extra for checking everything [he wanted the cost of the time refunded]
guess the two word reply!

In high performance engines the amount of cycles would be used as a measure of spring life expectancy if they did not show measurable degradation before hand.Some would replace springs after 10 runs regardless, some may change more often some less often, it will come down to what the chief or the guy picking up the tab reckons is safe.

Cheers.

[cardo0]

You may be hunting a moving target. I don't expect there's a specific number that works for all springs on all cams. But owing a Spintron spring analyzer would help.

Good luck.

[MadBill]

My thought is that running only 0.060" from coil bind (accurately checked) reduces surge potential and so enhances spring life in apps running up to the spring's ability. If a spring is properly rated for the required durability at the recommended minimum height, there should not be significant load loss over a realistic service life.

[steve cowan]

Those 1277 valve springs I put in Brads thread were 0.060" from coil bind as per the engine builder /supplier measured up.
I rang him in a panic saying I got nothing to shim when time comes, he laughed and said call me when you wear them out, well I have called him but not because valve springs worn out.
I am thinking out loud hear but
I think coil bind lands where valve spring rate (lbs/in) as per application of cam lobe, rocker ratio, pushrod strength, rpm etc.

[BradH]

Also suppose I should ask how much using a spring w/ a flat-spring damper vs no damper might change things...

[ProPower engines]

My thought is that running only 0.060" from coil bind (accurately checked) reduces surge potential and so enhances spring life in apps running up to the spring's ability. If a spring is properly rated for the required durability at the recommended minimum height, there should not be significant load loss over a realistic service life.

I had the same talk with the guys at PAC regarding spring life and it was a case of running the spring a bit taller .100 from coil bind that was causing 6the issue but the lift at the valve required .040 more installed height.
We ended up going with a different spring in that case but another build was done the same but did not need the extra installed height. The result was springs breaking. After replacements were installed at the .050 from CB no more springs had issues.
The other option was to use a taller spring and move the rocker shafts up on the mounts and push rods etc etc etc for the extra lift on the other engine we started out with the extra coil bind clearance.

[MadBill]

I don't quite follow your description Pro. Can you rephrase what the set up was that caused breakage?

[ProPower engines]

We ran the springs with a little more installed height by .040-.050.
I did not think it would be an issue as there was enough seat and open to get the job done.
The engine broke a few springs after about 20-30 1/4 mile runs but when we changed up the valve train some and
ran them at THE RECOMMENDED INSTALLED HEIGHT as per PAC the issue was solved.
It was a case of using a spring not to its full potential so to speak as far as there installed height went.

It seems to be an isolated issue and have not had the problem any further but when told to decrease the installed height
it seemed funny that they would break with about 20 lbs less seat/open with the extra installed height. But broke a few
down the road. And after going with the min. installed height they have been fine since on both engines.

Just to be clear it was not the same spring number as the OP used it was just a case of stranger things can happen

[PRH]

I’m sure there are other threads on this subject here..... but it’s also been discussed over on YB several times.

[BradH]

I’m sure there are other threads on this subject here..... but it’s also been discussed over on YB several times.

That's pretty much what I meant when I said: "I've searched a number of threads here and elsewhere about this question and am seeing knowledgeable people respond both yes and no"

It SEEMS like the majority say it's better to run 'em close, but some folks who have waaaaaaay more experience than I do have also mentioned having issues that went away w/ a bit more clearance (e.g., .100").

And, yes, this is sh!t that I shouldn't let drive me a bit nutz over, yet it does...

[PRH]

Not to mention....... a few who were big proponents of the “.050 til bind” for just about everything....... no longer feel that way.

[modok]

Why set them loose? because your lazy?
If the spring surges, the coils will hit anyway, so it will be the same amount of stress on the spring and yet giving you less force.
in order to set the springs .010 per coil from bind.... you have to check ACTUAL lift, and ACTUAL coil bind, which is more work.
One question that I am not sure of... is the case of some beehive springs, the coils do not bind at once.
It takes quite considerably more force to fully compress the top smaller coils, and nobody is quite sure if they need to be compressed or not to be defined as bind or what to make OF that.

[rustbucket79]

Years ago we bought a top end kit and cam from a well respected US engine shop. During the head assembly I found I had maybe .050” clearance including lash. I called and talked to their person in charge of their cylinder head program. He basically said with deflection the rated lift never happens, I had lots of room.

[digger]

Why set them loose? because your lazy?
If the spring surges, the coils will hit anyway, so it will be the same amount of stress on the spring and yet giving you less force.
in order to set the springs .010 per coil from bind.... you have to check ACTUAL lift, and ACTUAL coil bind, which is more work.
One question that I am not sure of... is the case of some beehive springs, the coils do not bind at once.
It takes quite considerably more force to fully compress the top smaller coils, and nobody is quite sure if they need to be compressed or not to be defined as bind or what to make OF that.

Anyone plotted force vs displacement?