Personally I'd use single valve springs, you should still have plenty of spring pressure.

 

But yeah 9000rpm is quite a lot haha. According to some K's reach a harmonic point at 8000.

I do know someone that had a 3K that reved past 10,000 though

 

I see what you're saying with the spring pushing on the cam, but with higher spring pressure comes more friction, on the cam/cam followers and cam bearings etc.

Friction is power loss

The dual springs are to eliminate the natural resonance you get with any spring, not to add any extra pressure on the valve.

 

Valve bounce will come from the harmonics of the spring at a certain rev range, so you add a sprng that doesn't have bounce at those revs.

Probably the best advice is: don't get too carried away with seat pressures and double valve springs, you can use up HP to open and close valves and also increased valve train wear.

 

 

Does anybody have another opinion on the high seat pressure using power topic? I

 

There's a common misconception that doubles = high spring pressures.

 

I did the calcs for my Crow 4220's; starting with the same seat pressure as stock, the nose pressure is less. Duals have a lower spring rate, so by the time you increase lift you can still end up with less nose pressure!

 

My concern was that I might have to low a seat pressure given my large cam!

 

Again - this is not a "rule of thumb". I calculated all my pressures myself and I checked and rechecked. Honestly, anyone building their own motor should be doing the same, as each application will differ. My biggest problem was spring bind because of my lift, and Duals were the only option without doing machining.

Where running Holden 202 springs in out speedway car, We run out of grunt at about 8000 and have no problems with valve bounce

Where running Holden 202 springs in out speedway car, We run out of grunt at about 8000 and have no problems with valve bounce

Did you need to machine the spring seats to use the 202's?

we have commadore ones I'm pretty sure and seem good

Did you need to machine the spring seats to use the 202's?

 

 

I'm not sure as my head bloke does it all, Good news is I dropped a head in there last week I will ask when I pick it up in a few days.