Valve springs question.

[Badasspen]

So I started taking down the heads to have a look at the bowls to see what I can do to help them along. I have a set of double springs that I would like to use. I noticed that the geometry will most likely limit me in my cam choices. Which springs do I use? Here are my bench top specs.
Intake , open 1.982. Compressed 1.135
Exhaust, open 1.775 Compressed 0.985
Double Springs open 2.215 Comp. 1.285
I know higher springs will accommodate less lift, however lighter springs tend to float at high RPM. What's the skinny?

 

[Locomotion]

I'm gonna stick my neck out and guess that you measured the springs "loose", off of the engine.

Get the spring recommendations for the cam from the cam manufacturer and the installed (closed valve) height and compressed (open valve) height @ max lift of them. The spring height at max lift (compressed at max cam lift) must be at least .060" less than the "coil bind" height of the spring. These measurements have to be taken on the head as assembled and there are a lot of variables that will influence those numbers. (i.e.: valve length, valve jobs, different spec locks & retainers, machined valve pockets)

You won't know if the dual springs you have will work unless you have their part # & specs. A spring pressure tester would be the most accurate, especially if they are used.

You are correct that lighter springs will promote valve float. Heavier springs can provide more lift & rpm, depending on their specs, installed height, etc., but heavier than needed for the combination can wear out the cam lobes.

It's pretty complicated.

 

[F body Deconstructor Jim]

What he said....and more.
Also...to use the double springs you'll have to have some machining done on the guide boss and spring seat.

 

[AJ/FormS]

Yeah I agree, complicated. But the big questions are, what are you working on, and where are you going with it? or is that information in another thread that I missed?

Springs have a tough job. They are rated at an installed height and at a certain open height. The free length has only a minor role in things. But the fully compressed height is very important , and you have to stay away from that with your cam's lift.
To get an idea of what installed height you have, you can measure it! Simply install a retainer with locks and measure between it and the spring seat. This is just one measurement of many, and by itself means not much, cuz you can bet a looney, you won't find a spring spec to work at your exact measurement.
Myron's right, complicated stuff. And if you blow it,and you're lucky,the engine just runs poor for a bit and recovers. But if you blow it bad,stuff wears out prematurely, or stuff breaks. When it breaks it usually takes the whole engine with it!, so don't blow it bad.....