When I get home tonight, I'll post some info on springs.
As for seals, ditch the umbrellas and go with Teflon seals. They seal much better, won't slide up, and they last ten times longer. You can use either .530 or .500 seals, but you will have to take the head to your machinist to have them installed. I'll post a pic of them tonight.
Here is a pic of the .500 Teflon seal.
And here's a pic of the dual spring setup I stock.
You have many choices for springs. Single, single with a damper, or dual spring, all with various rates. Springs are rated by the closed (on the seat) pressure, open pressure, and coil bind (lift). Stock single springs range from 52-80lbs closed and 114-200 open. Aftermarket springs for our small sixes will range anywhere from 60-120lbs closed, to 175-260lbs open.
Most cam manufactures will recommend a single spring with a damper, or a dual spring setup. Mainly because they offer higher spring rates with less coil bind (more lift), and for increased safety. If you only have a single spring and it breaks, the valve will partially drop into the cylinder, which can cause catastrophic damage.
Here are the three spring combos I stock:
Single spring with damper - for cams up to 260 duration
Closed 80lbs - Open 167lbs @.500 lift - Coil bind .925
Single spring with damper - for cams 260-280 duration
Closed 100lbs - Open 180lbs @.500 lift - Coil bind .925
Dual spring - for cams 270-300 duration
Closed 110lbs - Open 260lbs @.500 lift - Coil bind .925
All three come with a one piece retainer and Teflon seals (as pictured above) and require machining to remove the step and to install the seals.
Hope that helps.
