Cam manufacturers and valve spring requirements

[S14toRPS13]

It makes sense that cams with longer durations and higher lifts would require stiffer valve springs. So why do some companies recommend upgrading valve springs while others don't? There are some examples below of what I'm talking about. They're all SR cams as that's what I have.

Cams that don't require valve springs according to manufacturers:Tomei Poncams 256/256 11.5mm liftBC 264/264 12.06mm liftHKS 256 10.5mm liftHKS 264 10mm liftGreddy 256/264 10.5mm lift

Cams that requires valve springs according to manufacturers:Toda Cams 256/256 10.5mm lift and upTomei Procams 260/260 12mm lift and upHKS 264 11.5mm lift and up

Tomei and BC are saying valve springs aren't required for an 11.5mm lift and 12.06 lift while Toda and HKS is saying valve springs are required for a 10.5mm lift and a 11.5mm lift. Tomei also requires valve springs for a 12mm lift while BC still doesn't require valve springs for a cam with a longer duration and a higher lift. This makes no sense to me. Is it just marketing tactics by the companies or is there something else that I'm missing here?

[kouki munster]

Cam ramp rates also play a part in whether or not you will need stiffer springs, so a higher lift longer duration cam with a mild ramp rate won't require springs that are as stiff as a cam that has less lift and duration with an aggressive ramp rate.

Look at the ramp rates as how fast the valves are being opened and how fast they are being allowed to close, the faster it gets opened the more momentum it has when it reaches max lift, so the spring will have to with stand more force to keep the control of the valve, and the faster the cam profile allows the the valve to close the more energy the spring will need to keep the valve following the cam profile.

But, I don't think any of thoes companys list ramp rate info for their cams, they just recomend you have stiffer springs for X cam.

[S14toRPS13]

Very well explained!

[kouki munster]

Not a problem, I do what I can.