You can't say it much better than that. There is a harmonics effect but more important you need to get the correct springs for your particular cam, period 
Theory Question: Valve Spring Oscillation
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Racer
Joined: Dec 2008
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From: Toms River NJ
Theory Question: Valve Spring Oscillation
Just picked up a new set of heads, and they have springs that are good to .800" lift. I prob wont run a cam with anywhere near that much lift (prob be around high .500's lift), so I thought this would be fine. A mechanic friend of mine told me that going with a cam that is too small may cause valve spring oscillation due to the harmonics caused by not bring the spring close enough to its binding point. or something to that effect. He told me to look it up. I did. I found nothing. He then said it had something to do with the base circle of the cam. He's a young guy (might not know what he's talking about), but he's GM certified (should know what he's talking about). Is there anything to this?
Thanks in advance for your help.
-Dan
Thanks in advance for your help.
-Dan
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
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Current thinking has us working springs as close to coil bind at max lift without actually stacking them. They last longer that way.
But any cam with .500's lift is not going to like springs designed for .800 lift.
Tell us what you're building and what you're going to do with it.
Sounds like fun already!
JIM
But any cam with .500's lift is not going to like springs designed for .800 lift.
Tell us what you're building and what you're going to do with it.
Sounds like fun already!
JIM
Thread Starter
Racer
Joined: Dec 2008
Posts: 300
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From: Toms River NJ
Current thinking has us working springs as close to coil bind at max lift without actually stacking them. They last longer that way.
But any cam with .500's lift is not going to like springs designed for .800 lift.
Tell us what you're building and what you're going to do with it.
Sounds like fun already!
JIM
But any cam with .500's lift is not going to like springs designed for .800 lift.
Tell us what you're building and what you're going to do with it.
Sounds like fun already!
JIM
So the verdict is to match cam and springs. I have 2 sets of springs, the ones that are on the heads (Manley Nextek .800 max lift), and the guy threw in the orig springs for the AFR heads (max lift .670). Im not made of money, so now I guess Ill be matching my cam to my springs. Higher lift, here I come.
Thanks for help guys!
-Dan
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I bought my set of AFR 227's from AFR without the springs. They actually wanted more money for the heads minus the springs, ( salesman added up all the parts ) after a bit of yelling at them they gave me some money off.
Are your heads the new Eliminator heads or the previous version ?
Are your heads the new Eliminator heads or the previous version ?
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Lift allowance isn't the only concern. The installed height, spring load at installed height and spring rate are also very important to match with the cam manufacturer's recommendations. The easiest way to accomplish this is to just buy the exact springs specified by the cam co. Why play guessing games with something so important?
Thread Starter
Racer
Joined: Dec 2008
Posts: 300
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From: Toms River NJ
I bought my set of AFR 227's from AFR without the springs. They actually wanted more money for the heads minus the springs, ( salesman added up all the parts ) after a bit of yelling at them they gave me some money off.
Are your heads the new Eliminator heads or the previous version ?
Are your heads the new Eliminator heads or the previous version ?
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Installing springs to within about .010 per coil revolution is the current train of thought, as Jim said.
Beehives help a lot as do ovate wire springs, both help reduce oscillation.
If you ever get a chance to watch a high speed shot of a spintron, it'll surprise you what's going on in your valvetrain. NO valve really seats at higher rpm's, they all bounce until the next lift cycle.
Beehives help a lot as do ovate wire springs, both help reduce oscillation.
If you ever get a chance to watch a high speed shot of a spintron, it'll surprise you what's going on in your valvetrain. NO valve really seats at higher rpm's, they all bounce until the next lift cycle.
Thread Starter
Racer
Joined: Dec 2008
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From: Toms River NJ
Lift allowance isn't the only concern. The installed height, spring load at installed height and spring rate are also very important to match with the cam manufacturer's recommendations. The easiest way to accomplish this is to just buy the exact springs specified by the cam co. Why play guessing games with something so important?
So now to make some calls to Manley and AFR and see if I can get some more specs on my springs. Then to call Comp or Lunati and wax technical with one of their tech guys.
-Dan
Thread Starter
Racer
Joined: Dec 2008
Posts: 300
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From: Toms River NJ
Installing springs to within about .010 per coil revolution is the current train of thought, as Jim said.
Beehives help a lot as do ovate wire springs, both help reduce oscillation.
If you ever get a chance to watch a high speed shot of a spintron, it'll surprise you what's going on in your valvetrain. NO valve really seats at higher rpm's, they all bounce until the next lift cycle.
Beehives help a lot as do ovate wire springs, both help reduce oscillation.
If you ever get a chance to watch a high speed shot of a spintron, it'll surprise you what's going on in your valvetrain. NO valve really seats at higher rpm's, they all bounce until the next lift cycle.
and, just to clarify, installing springs to within about .010.... of what?...per coil revolution
-Dan
Team Owner
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Your mech friend doesn't understand base circle has nothing to do with with the springs. .800 lift is for big spring pressure roller cams
Any competent head shop can tell you @ what a given set of springs are.
They compress them to installed height and read off the closed pressure then compress the spring .5 inches and give a spring rate in pounds.
Then compress it to your valve lift to give you open pressure.
Common wisdom is to use as much free coil space as practical to make the springs run cooler and last longer.
On the other hand race motors use very little coil clearance like .030 total before bind to act as a mechanical stop. So if a valve floats it can never have valve to piston contact in a very tight tolerance motor. This only applies to racing motors that change the springs quite often
Are you planning to do 8000 rpm with your little 383 crate motor? Because that is what those heads are made to do on small motors Those require big port single plane intakes and large tube headers. They are also intended to run big .700 lift cams that why it had those big springs
Any competent head shop can tell you @ what a given set of springs are.
They compress them to installed height and read off the closed pressure then compress the spring .5 inches and give a spring rate in pounds.
Then compress it to your valve lift to give you open pressure.
Common wisdom is to use as much free coil space as practical to make the springs run cooler and last longer.
On the other hand race motors use very little coil clearance like .030 total before bind to act as a mechanical stop. So if a valve floats it can never have valve to piston contact in a very tight tolerance motor. This only applies to racing motors that change the springs quite often
Are you planning to do 8000 rpm with your little 383 crate motor? Because that is what those heads are made to do on small motors Those require big port single plane intakes and large tube headers. They are also intended to run big .700 lift cams that why it had those big springs
Last edited by gkull; Mar 30, 2009 at 06:43 PM.
Thread Starter
Racer
Joined: Dec 2008
Posts: 300
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From: Toms River NJ
...Common wisdom is to use as much free coil space as practical to make the springs run cooler and last longer.
On the other hand race motors use very little coil clearance like .030 total before bind to act as a mechanical stop. So if a valve floats it can never have valve to piston contact in a very tight tolerance motor. This only applies to racing motors that change the springs quite often
Are you planning to do 8000 rpm with your little 383 crate motor? Because that is what those heads are made to do on small motors Those require big port single plane intakes and large tube headers. They are also intended to run big .700 lift cams that why it had those big springs
On the other hand race motors use very little coil clearance like .030 total before bind to act as a mechanical stop. So if a valve floats it can never have valve to piston contact in a very tight tolerance motor. This only applies to racing motors that change the springs quite often
Are you planning to do 8000 rpm with your little 383 crate motor? Because that is what those heads are made to do on small motors Those require big port single plane intakes and large tube headers. They are also intended to run big .700 lift cams that why it had those big springs
I'm aware of the RPM implied by this combo. At the track I'll probably shift around 7 grand and just let the rest of the curve go to waste. On the street, its just going to be a dog (relatively).
Thanks for your input
-Dan
Drifting
Joined: Aug 2004
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From: Lubbock TX
dp9, .010 per coil means that if your spring has 7 coils/revolutions, you'll install the spring at full lift .070 short of coil bind/stack. Sounds like your heads are set up for a big solid roller - what are the specs on the cam you are going to be running?
Team Owner
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From: Reno Nevada
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I want my springs to last and run cooler with my higher lift solid roller cams. So I use Comp Cams springs rated for say about .800 max lift and then only lift the valve .700 so I'm not stressing the springs
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Maybe this will help you.
Crane clearly states .060 or (MORE) coil clearance our racing American v-8's at the shop are often .100 or more clearance and the exotic foreign v-12's and multi cam motors are the ones that use coil bind to prevent valve float. but that is in up to 12,000 rpm motors
http://www.cranecams.com/?show=valveSpringsFAQ
Crane clearly states .060 or (MORE) coil clearance our racing American v-8's at the shop are often .100 or more clearance and the exotic foreign v-12's and multi cam motors are the ones that use coil bind to prevent valve float. but that is in up to 12,000 rpm motors
http://www.cranecams.com/?show=valveSpringsFAQ
Thread Starter
Racer
Joined: Dec 2008
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From: Toms River NJ
I called AFR today and inquired about a rumor I had heard on the yellowbullet board. AFR confirmed that their 227 heads actually have aprox. 218cc intake runners (race ready), or 223cc (competition ported). They also were kind enough to give me specs for the springs I have. the .670 lift springs - 225 load on the seat, 550/inch rate. the .800 lift springs - 235 load on the seat, 535/inch rate.
Havent picked out a cam yet. Since the heads are a little smaller than I originally thought (which is a good thing), I'm going to go with a cam that gets me to my desired lift in the shortest amount of duration possible, without exceeding the spring rate. I do know that I'm looking for a hydrolic roller with at least a 113* LSA. Ive got a rev kit to get the HR cam past 6500rpm, and the wide LSA is for added vacuum at idle, and because an EFI swap might be in the works.
-Dan
Thread Starter
Racer
Joined: Dec 2008
Posts: 300
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From: Toms River NJ
Maybe this will help you.
Crane clearly states .060 or (MORE) coil clearance our racing American v-8's at the shop are often .100 or more clearance and the exotic foreign v-12's and multi cam motors are the ones that use coil bind to prevent valve float. but that is in up to 12,000 rpm motors
http://www.cranecams.com/?show=valveSpringsFAQ
Crane clearly states .060 or (MORE) coil clearance our racing American v-8's at the shop are often .100 or more clearance and the exotic foreign v-12's and multi cam motors are the ones that use coil bind to prevent valve float. but that is in up to 12,000 rpm motors
http://www.cranecams.com/?show=valveSpringsFAQ
...I probably should've started there.
-Dan