Valve spring coil bind clearance
Valve spring coil bind clearance
I'd like to read some pro opinions on minimum coil bind clearance with Beehive springs. I've mostly read that .060" is the minimum but also have read that less is still ok. I read that coil contact without binding is good for dampening. I'll post 1 article that can read first before you reply. Scroll down to "Installation issues"
https://www.enginebuildermag.com/2010/01/performance-valve-springs-and-retainers/
https://www.enginebuildermag.com/2010/01/performance-valve-springs-and-retainers/
Last edited by Brads1971; Jul 20, 2021 at 09:55 PM.
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Coil bind" occurs when a spring's coils stack solid at or before full camshaft lift. This develops an infinite load on the valve train, causing its weakest link to fail. If you're lucky, the result is just a bent pushrod; otherwise, you're looking at a broken spring, a dropped valve, or worse.
When installed at the correct height to develop the right seat and open pressures for the application, a spring needs to have a safety margin before coil-bind occurs. The formula used to determine whether a spring has sufficient coil-bind clearance is: valve spring installed height on the seat (cam lobe lift rocker arm ratio) + valve lash safety margin = remaining open spring length, which should be equal to or greater than the spring manufacturer's published coil bind height.
About 0.060 inch used to be the textbook safety margin, with more OK and even desirable. That's still an acceptable standard for everyday performance use, but for cutting-edge setups the "correct" safety margin can vary up or down. Comp Cam's Billy Godbold notes that "from high-speed video and testing, it is clear that adjacent coils contact as you approach the valve train-limiting speed (this is known as spring surge). Hence, modern springs are designed to run near coil bind and use the coil-to-coil interaction for improved damping at or near max lift. This interaction is one of the most effective means of dampening spring surge, but the spring must be properly designed in terms of solid stress to safely use this interaction." Depending on the intended use and the spring and cam-lobe design, coil-bind safety margins can now vary from 0.015 to 0.120 inch, with tighter numbers predominating on very stiff valve trains. Anything more than 0.150 inch may cause spring surge, which can greatly reduce the available spring load needed to close the valve.
clip/paste
When installed at the correct height to develop the right seat and open pressures for the application, a spring needs to have a safety margin before coil-bind occurs. The formula used to determine whether a spring has sufficient coil-bind clearance is: valve spring installed height on the seat (cam lobe lift rocker arm ratio) + valve lash safety margin = remaining open spring length, which should be equal to or greater than the spring manufacturer's published coil bind height.
About 0.060 inch used to be the textbook safety margin, with more OK and even desirable. That's still an acceptable standard for everyday performance use, but for cutting-edge setups the "correct" safety margin can vary up or down. Comp Cam's Billy Godbold notes that "from high-speed video and testing, it is clear that adjacent coils contact as you approach the valve train-limiting speed (this is known as spring surge). Hence, modern springs are designed to run near coil bind and use the coil-to-coil interaction for improved damping at or near max lift. This interaction is one of the most effective means of dampening spring surge, but the spring must be properly designed in terms of solid stress to safely use this interaction." Depending on the intended use and the spring and cam-lobe design, coil-bind safety margins can now vary from 0.015 to 0.120 inch, with tighter numbers predominating on very stiff valve trains. Anything more than 0.150 inch may cause spring surge, which can greatly reduce the available spring load needed to close the valve.
clip/paste
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Agree with the .060 requirement. I can't think of any situation where coil bind is safe, much less desired. And you need to take valve stem seals into consideration too. Valve spring selection should be based on the cam profile and intended use of the vehicle. But it's best to keep valve seat pressure as low as safely possible because it puts added strain on everything from the rocker down, and required HP to overcome that pressure. Too much seat pressure will beat the valve seats and wear out seats and valves prematurely.
Paul
Paul
Thanks guys, I got it sorted out. My springs are good with my .659" lift. I have .060 between coils near the top plus maybe .010 - .020 between the next coils above.
My heads have 1.98 intake and 1.61 exexhaust valves and are flowing 280 cfm @ 28.
My heads have 1.98 intake and 1.61 exexhaust valves and are flowing 280 cfm @ 28.
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From: deland,florida
That's not how you check for coil bind
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