After lots of research on my planned Scorpion 1.7 RR install, there are still a few things I am uncertain of. I know the two issues I need to be concerned about with the springs are, Valve Float and Spring Binding.

As I understand it, Valve Float happens when the RPMs are high enough, not allowing the valve to completely close before the cam has made a full revolution, and the rocker starts to open the valve again. Is this correct? If so, the only way I see to determine if the right springs are being used is to compare the spring pressures with what is required to close the valve completely before a full revolution of the cam. How is this done? I know I can find spring pressures from the manufacture's specs; but how can I determine what is required at what RPMs to avoid float?

As I understand it, Spring Binding is when the total realised lift of the valve is greater than the spring is rated for, and the spring bottoms out. If this is true, then I just need to make sure the spring I am using (Comp 987s) can handle the lift I should get with my setup (.507 / .520). Is this corret? If so, I shouldn't have to worry about bind considering the 987s are rated to .600.

Regards,
Thomas.

 

that sounds about right

effectively, valve float is when the spring is unable to force the valve closed as fas t as the lifter is droping on the back of the cam lobe,therefor, the valve is floating free of the lobe

spring bind/coil bind is just as you said, it is the amount of lift required to collapse the spring until the coils touch, you want to stay away from this number by a fair amount, I have heard 0.020 , so if you have .500 lift, you want springs that will not bind at less then .520 lift

 

I'm gonna write this on the old mans account...

Valve Float is more accurately labeled as Valve Bounce 90% of the time. The bounce happens as the valve closes and the motor looses the trapped volume of air and you loose power. You can also have float if the cam is too aggressive over the top and things start becoming unstable. Once they become unstable you have to slow everything back down to gain control again.

Spring Bind is where the coils all stack up and become soil. This is the coil bind height of the spring. If your installed height minus max lift is less than the coil bind height the spring goes BOOM.

Bret

 

Thanks for the info guys.

So how can you be sure the spring you choose has enough pressure (seat load or open load?) to prevent Valve Float/Valve Bounce?

The 987s list Seat Load as 121@1.800 and Open Load as 388@1.200. I assume these numbers should be compared to some pressure # which can be determined from the valvetrain setup. Is this true? Or do you use the Rate spec (344 lbs/in for 987s) to determine this?

I notice the spring manufacture's spec sheet has a Coil Bind number. What exactly is this #? The 987s list Coil Bind as 1.15, but are supposed to handle lift to .600. I'm a bit confused as to how these numbers relate?

I think I should be alright as far as coil bind/spring bind, because the 987s are rated to .600 lift and I will only be pushing .520 max on the exhaust. Is this a fair assessment to make?

Thanks again guys, great info!
Thomas.

---------------- edit ----------------
Ahh, it just clicked The coil bind number (1.15) is the height at which the spring will bind. The max lift (.600) is the maximum amount the coil can compress before reaching the bind number.

So taking the install height, minus the max lift will give you the minimum height the spring will reach; and if this is smaller than the coil bind #, you are in trouble!

Is that about right?