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Sat Nov 28, 2015 7:46 am

How do you measure coil bind?

What is an acceptable clearance between the coils?

Does the gap between every coil have to be measured?

Thanks

Sat Nov 28, 2015 8:23 am

You measure the length of the spring when it won't compress anymore. Dan

Sat Nov 28, 2015 9:05 am

Put it in a vise or a Rimac type spring pressure tester and compress it until it won't move anymore then measure the length.

Sat Nov 28, 2015 10:54 am

lets assume that the springs and valves are installed in the head.

Sat Nov 28, 2015 11:02 am

Just dont assume what you have at coil bind "cold" is the clearance you have to work with. That is minimum coil bind.

As the parts get hot they expand. I would add a minimum of about .040" of extra space. Some say more...some say less depending on experiences. Ray

Sat Nov 28, 2015 11:15 am

Ray Greenwood,

The .040" clearance that you are referring to, is that at every gap between coils?

It seems that the coils at the top & bottom of the springs have a closer gap than the middle of the spring.

Sat Nov 28, 2015 11:45 am

VW&MGman wrote: Ray Greenwood,

The .040" clearance that you are referring to, is that at every gap between coils?

It seems that the coils at the top & bottom of the springs have a closer gap than the middle of the spring.

This is a good course of study to kind of understand what coil bind is and how it acts. Not all springs are "single" rate...meaning by design some can be "progressive". This means that looking at them when they are "free" and uncompressed sitting on the counter you may notice that that not all coils have equal spacing or even equal cross section.
These variations allow tuning of spring rates by the manufacturer. Also...springs that are ground flat at each end....those ground off coils have less tension to offer so will compress sooner than the full coils in between. I have no idea what springs you have.

All of that aside...

Slowly compress the springs and observe. Yes....some of the end coils may start moving together sooner than coils in the middle or at the other end.

This is not YET coil bind. Even if coils somewhere in the spring begin to make contact with each other early....effectively acting like a solid....the coils elsewhere in the spring will continue to move closer together allowing further compression in the coil.
So the real simple answer would be too have .040"-.060" of slack somewhere...anywhere in the coil. Like...take it to coil bind and then back off so .040" of space appears somewhere.

That is also overly simple. The twist rate or angle of the coils in certain types of springs...can be changed enough as coils begin to lock up that it can cause severe misalignment of the spring or excessive friction between coils or even harmonic problems.

Most valve spring manufacturers should have some idea of what kind of spacing/tolerance above coil bind their springs run the safest with. I would ask if you have something exotic. Ray

Sat Nov 28, 2015 12:00 pm

Hi Ray,

Thank you for your informative response.

I purchased an engine kit from DRD with L6 heads. The heads were assembled with the springs and valves together. So I'm not sure exactly what brand of springs or specs they are.

I'm doing a mock-up of the engine and I'll measure the distance between the spring coils and report back.

Sat Nov 28, 2015 2:32 pm

Do some research online. There are some good articles out there.....hot rod magazine...circle track....comp cams among the many.

They note that .060" is in the general builders world the most common generic safety margin at full lift.

An article I read in Hot Rod also noted that modern valve springs in modern cars...which includes many racing vehicles.....are actually designed to run with coil clearance very near coil bind in high rpm applications and use the harmonics created from close coil proximity as part of the damping system.

Some of these use coil bind safety margins of as small a .015" up to .120"....but only in very well calculated and tested configurations.....because also its widely held that having really excessive coil bind safety margin...like .150"....can call what is called spring surging.....wherein the spring has a hard time building the correct seating/return pressure to control the valve.

If these are just basic single valve springs...I would say that between .040" to .060" would be plenty safe.

Alsom...check each spring with its retainer and any shims once you s3t everything up.....for correct tension at max lift. Just a few thousandths variation from valve pocket shims, keeper machine work and retainer machine work can make a significant difference. ...or n9t. You wont know umless you measure.
Ray

Sat Nov 28, 2015 4:33 pm

coil bind is when it stops compressing, no more no less, do not force it to "gain" more in your head, because you dont have it. most performance springs in a compitition setting need to be from about .030-.050 from coil bing for the lift being used(thats where they work best at keeping floaters away) a std car can be less, some springs you can messure the spacing some you cant.some will stack up and still have clearance on the other side. it's a good idea to check more than one spring.

Sat Nov 28, 2015 4:47 pm

Rig a dial indicator on the retainer, clamp big vice grips to a old rocker, compress the valve all the way and record the travel, if on the engine.

If not on the engine, use a drill press.

Sat Nov 28, 2015 8:30 pm

Geeze.. you guys done confused the fella.

Yes, coil bind is when you bottom out the springs, and measure that length. But more importantly, you want to know your maximum lift at the valve and compare that to the coil bind.

A Rimac is a nice tool to have. You can check your 'installed heights' and full lifts heights and check your spring pressures. Unless you are installing an FK89 cam on stock springs, I don' think you will have a problem. :D

So, bring the spring to full lift and stick a feeler gauge between the coils -the upper coils of the springs if variable, or if single rate anywhere. If you can stick a 0.040" feeler in there at full lift, you are good to go = NO COIL BIND.

You also want to check the retainers do not bottom out to the guides at full lift.

Hope this helps.

Sat Nov 28, 2015 10:07 pm

Most normal hi-po VW engines are not going to be anywhere near coil bind.

For example:
Have a set of Scat duals, factory 040 heads, and a Web 86b;
Started into measuring coil bind,
(smash them flat in a vice and measure overall length),
And did the math based on real measurements at full lift..

To get them to within .060 of bind at full lift required a whole big 'ol stack of those FSI shims you buy in the shrink-wrap;
Like a half-dozen of the thickest ones.
And this with stock-length valves..

The large stack of shims seemed to me to introduce more chance of a shim coming crooked, or chewing on the boss, because it required the stack to bring the base of the spring clear up above the spring pocket cut into the heads.
The spring being retained by the pocket is helpful in dampening harmonics supposedly, too.

In the end, I threw a couple of the thick shims in there, because it would still allow the spring to be reasonably retained, increase pressure a bit, and keep the spring from chewing on the head.
The springs are also likely to last longer if not required to go nearly to bind on every cycle.

Shimming to within .0X0 of bind is for race motors with long valves and .600 lift and other such seriousness.
If you really want to care, pull them off after a few thousand miles to make sure they aren't going away.

There are other motors that I build that get the valve spring shim treatment all the time.
A street driven beetle motor - not so much.