[Neil Harvey]

If I can add some info for you.

You are "measuring/calculating" the seat and nose spring pressures. Porsche realized most would not have the equipment to measure the actual pressures so they give an installed height that is an approx to the required pressures. Someone here has given the installed heights. Shims are available to obtain those heights. I cannot remember the thicknesses available, I think 0.010" and 0.020". You can buy Arbor shims as thin as 0.002" if you needed. But the shims from Porsche are what are considered close enough. No two new springs will have the same pressures v height.

Some important info here, you can expect the retainer heights to be between 1.300" and maybe as high as 1.500''. If the seats have been cut low, this height will be more towards 1.500".

If I was in the "bush", here is how I would do this. I would take a spring base and retainer to my local hardware store and buy a piece of PVC pipe that had an ID and OD that would fit the two pieces. I would buy a cheap drill index that went as high as 1/2" as well. Go home and cut the PVC to 1.250" as accurate as you can. Maybe run both end across some sand paper to true up the faces.

Fit this "spacer" between the base and retainer on each valve, to measure, with the locks fitted as well. Bottom out the retainer against the spacer with some slight force to seat the locks. Now use the drill bits as gauges between the spacer and the bottom of the retainer where the outer spring seats. The drill bit that fits snuggly is the size that gets added to 1.250". Covert to metric or convert the installed height required to imperial numbers and add shims to obtain these required installed heights.

Maybe this is helpful. You do what you have to when its required.