Valve spring coil bind
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
The beehive springs do actually collapse one coil onto another when they are being depressed, it is what helps keep mass out of the response. Not sure that what you have is not normal for a beehive design.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Here is a quote from Vizard's article, the whole article can be found here: Link
As for your issue, the spring likely lost stiffness and were having trouble controlling the valve train. If you still have them, you can verify their stiffness with a spring tester.
With a conventional spring we find that, other than the top and bottom coil, all the coils are evenly spaced. When the valve opens the top coil moves the same amount as the retainer/valve while the bottom coil remains stationary. Checking the motion of individual coils between reveals each moves proportionally less than the one above it. This means that during the opening event the rocker is not accelerating the entire mass of the spring but only a proportion of it. Determining the equivalent proportion being moved through the entire valve lift involves some relatively complex mathematical calculations. However, most textbooks on the subject indicate that the effective spring mass, as seen by the rocker, is typically one-third of the spring’s total mass.
An example here would mean that the mass of a typical 120-gram spring reacts as if it were 40 grams. During the opening event the coils get closer together but, even at full lift, they should not touch. If the coils do clash due to surge the stresses in the spring can spike to two and three times that induced during normal operation and failure will result.
The mode of operation of a beehive spring is somewhat different to that of its conventional counterpart. From the photos you can see the beehive spring’s coils become progressively smaller from the base to the top. For a given wire diameter the smaller a spring’s coil diameter gets the stiffer it becomes. Because of this the beehive spring’s top coils are not only smaller and lighter, but also stiffer.
When installed the coils nearest the spring seat – being less stiff – compress more than those at the top. As the spring is compressed during the opening of the valve, each coil progressively settles down onto the one below. As soon as any part of a coil has settled on the neighboring coil beneath, it is removed from the equation as far as mass in motion and spring rate is concerned.
By the time a valve controlled by a beehive spring reaches full lift only the small top coil or two is actually being moved and the springs stiffness has escalated considerably. Under these circumstances the remaining active coil or coils are very stiff in relation to the moving mass involved. In basic terms this means as the valve approached full lift the effective spring mass moved by the rocker is as little as 10 percent of the spring’s total mass.
As for your issue, the spring likely lost stiffness and were having trouble controlling the valve train. If you still have them, you can verify their stiffness with a spring tester.
With a conventional spring we find that, other than the top and bottom coil, all the coils are evenly spaced. When the valve opens the top coil moves the same amount as the retainer/valve while the bottom coil remains stationary. Checking the motion of individual coils between reveals each moves proportionally less than the one above it. This means that during the opening event the rocker is not accelerating the entire mass of the spring but only a proportion of it. Determining the equivalent proportion being moved through the entire valve lift involves some relatively complex mathematical calculations. However, most textbooks on the subject indicate that the effective spring mass, as seen by the rocker, is typically one-third of the spring’s total mass.
An example here would mean that the mass of a typical 120-gram spring reacts as if it were 40 grams. During the opening event the coils get closer together but, even at full lift, they should not touch. If the coils do clash due to surge the stresses in the spring can spike to two and three times that induced during normal operation and failure will result.
The mode of operation of a beehive spring is somewhat different to that of its conventional counterpart. From the photos you can see the beehive spring’s coils become progressively smaller from the base to the top. For a given wire diameter the smaller a spring’s coil diameter gets the stiffer it becomes. Because of this the beehive spring’s top coils are not only smaller and lighter, but also stiffer.
When installed the coils nearest the spring seat – being less stiff – compress more than those at the top. As the spring is compressed during the opening of the valve, each coil progressively settles down onto the one below. As soon as any part of a coil has settled on the neighboring coil beneath, it is removed from the equation as far as mass in motion and spring rate is concerned.
By the time a valve controlled by a beehive spring reaches full lift only the small top coil or two is actually being moved and the springs stiffness has escalated considerably. Under these circumstances the remaining active coil or coils are very stiff in relation to the moving mass involved. In basic terms this means as the valve approached full lift the effective spring mass moved by the rocker is as little as 10 percent of the spring’s total mass.
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Racer
Joined: Jun 2009
Posts: 326
Likes: 0
From: Texarkana TX
valve float can also leave those kind of marks, and leads to a loss of upper rpm power...and beehive springs do collapse progressively, comp has an artical somewhere you can check out...just my $0.02
Chuck Priestly
ASE Master Engine Machinist
Warrior Performance Inc.
Best Engines
Chuck Priestly
ASE Master Engine Machinist
Warrior Performance Inc.
Best Engines
Last edited by warriorp; Nov 1, 2009 at 10:25 PM.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
They weaken over time and you were likely losing control of the valve train so you saw an issue at lower RPM. In a way you were fortunate and smart enough to check it out as there have been a number of the yellow springs break and in some instances they took the motor with them.
Did you install new GM springs or go aftermarket? If you installed GM, I am curious if they were still the yellow springs and said "Made in Germany" on them? I used these to rebuild my 241 heads and the fact that there have been a number of failures has me a little spooked.
Did you install new GM springs or go aftermarket? If you installed GM, I am curious if they were still the yellow springs and said "Made in Germany" on them? I used these to rebuild my 241 heads and the fact that there have been a number of failures has me a little spooked.
Team Owner
Joined: Jan 2004
Posts: 22,185
Likes: 65
From: NJ
Coil bind is a variable you can check for right up front and usually isn't something that happens over time. Its the result of bad set up right up front.
Last edited by Chevy Guy; Nov 2, 2009 at 10:14 AM.
Advanced
Joined: Apr 2005
Posts: 65
Likes: 0
Spring coil clearance should be set up when they are installed. You get the installed height and pressure specs and put them in a tester, get your opening spec of your cam shaft and compress the spring to that measurment and then check your coil clearance. It can be adjusted by shims during the set up. The min proper clearance is about .070. I like the Comp 921 springs as they have dual springs so when you break one you save the piston. I am running a .667 lift cam with 912 springs and I have .057 clearance, close, but I can't machine the AFR heads for any more. On the LS6 motor the hollow stems help to control the valve float. If you change to aftermarket rockers, which you have, you will have valve float past 6800 rpms. I have tried several brands and I keep going back to LS6 rockers with aftermarket bearings(Harland Sharpe) in them. You can see the valve float past 6800 on the dyno. After switching back every time to the LS6 rockers the dyno sheet shows better valve train control at those rpms. You were using stock springs with those aftermarket rockers and you were getting float, that was the marks on the springs.
Race Director
Joined: Nov 2000
Posts: 10,340
Likes: 664
From: Beverly Hills (Pine Ridge) Florida
Also, since you are running a supercharger, that puts increased pressure on the intake springs. The intake springs are trying to close the valves, while the boost pressure is trying to keep the valves open. Recommend increasing the spring pressure to "compensate".
Plasticman
Plasticman
Racer
Joined: Dec 2006
Posts: 343
Likes: 1
From: LasVegas Nevada and NSW Aust
I have just had some simalar issues and am investigating the cause. I put 243 ported and polished heads with 224/228 lsa 114 in my vette last week and had it on the dyno and experianced vallve float at 6000rpm. I have comp cams double valve springs stdard ls6 rockers and ls6 7.4" push rods. The tuner seems to think my push rods are short as we can here a bit of valve train noise. The car made 387rwhp at 6000rpm befor experiancing valve float and the tuner says it should be making power to 6500rpm.
Planning on checking pushrod length this weekend, if thats ok looks like i will have to replace valve springs even though they are new.
Planning on checking pushrod length this weekend, if thats ok looks like i will have to replace valve springs even though they are new.
