How do the experts pick the right valvespring?

[Kern Dog]

I'm sitting here pondering the purchase of some quality roller tip adjustable rocker arms and the thought of valvesprings came to mind.
My Edelbrock heads are supposed to be fitted with springs rated to .600 lift. I'm considering a switch to 1.6 rocker arms that will bump my lift to .543. I see that I am well below the point of coil bind, but what other factors figure into the whole thing? I have the MP 292/509 hydraulic cam in an engine that rarely sees more than 6200 rpm.

 

[Photon440]

A couple of other factors that will play a part would be the intended RPM (which you mentioned) and the weight of the valves and associated valve train. Hollow valve stems, titanium valves, or light weight rockers will all affect when the spring has reached it's limit.

Your .600 lift is one thing, but how FAST it ramps up and closes is another.

 

[Cranky]

A couple of other factors that will play a part would be the intended RPM (which you mentioned) and the weight of the valves and associated valve train. Hollow valve stems, titanium valves, or light weight rockers will all affect when the spring has reached it's limit.

Your .600 lift is one thing, but how FAST it ramps up and closes is another.

You're absolutely right!

Even the retainers can make a difference. Most people I know don't use the springs that came with the Eddy heads and imo, it's best to talk with the cam manufacturer about what springs to use for their cam. Also, you can talk with custom cam grinders about 'your' combination. They may want to know if your valves and retainers etc are light weight or not. Generally, you can stay with the recommended spring but if you use for example a titanium retainer instead of steel, you can go a few hundred rpm higher. This is one reason why going with a custom grind is usually better than going with an off the shelf stick.

 

[99ss]

All good info above
The weigth of the valve-train makes a huge difference and the weight on the nose. DO you want a good single or doubles?

As cranky photon stated ramp rates makes a huge difference as well. Who ever grinds the cam should have a recommendation.
I run close to .700 lift with a marine application lobe and a PAC single.(in my Camaro) Lots of guys like to go to a double for the redundancy protection.

 

[Meep-Meep]

The springs really just close the valves and they have to do that smoothly. Factors like natural frequency of the spring itself and of the spring with all the hardware attached is very important because mass affects the natural frequency. The short answer is you don't want to be anywhere near the natural frequency of the valve train in the RPM range that you operate in. And after all the calcs are done I'm sure they run the setup on a dyno, even if it's just spinning the cam loaded with all the valve hardware by itself.

And this leads me to another comment about the 1.6 rockers. Why do you need them? Sure, they can make more power in the right application, but if you are just building a track car I would think the .509" cam with 1.5 rockers is plenty. As a matter of fact it is plenty good enough to run 12 flat in a B body - possibly better. Don't get hung up on lift as it's hardly a major factor in deciding the final outcome of your build. Rather focus on lobe separation (overlap), which in my opinion is far more important to get correct for the intended build. If you just want a street car that you intend to keep together for a long time and put a lot of miles on it the .509" is the wrong cam. If you want an occasional driver that is race tuned the .509" or similar cam will put a smile on your face for sure, but all that at the expense of higher valve spring pressures = wear and tear. There is a reason race engines are just that. They require frequent maintenance and sooner than later you will throw all the valve gear away and replace with new because it really takes a beating. My $.02 N E way.