I'm putting a new set of dual springs in my big block with a Udharold mecanical solid cam in it. His specs were 140lbs seat and 340 open.
I Rimaced this springs over lunch today and at my 2.000" installed height I would have 125 lbs and 350 open. With the .060 shim I had with the old springs, I would have 150 on the seat and 390 open. I did forget to bring a retainer with me, so it would pick up a little bit of pressure.

So am I better off putting them in with no shim for a closer open pressure, or with a shim so the seat is closer but with a higher open pressure. Or go pick up a 15 or 30 shim and split the difference. It is just my street car but the old springs were way too light and had valve float problems.

I would check it with the retainers and see what you have. Shims are availabe in .015/.030/.060".

If installed hieght is 2.00 than spring pressure won't change at 2.00 with the retainer. The cylinder head from spring pocket to retainer is 2.00"?

Installed height is 2.00" to to outside of the retainer, but theres that second ridge on the retainer that the inner spring rides on.

I guess what my original question really was is am I better off shimming for proper seat pressure with extra open pressure, or for proper open pressure with to little seat pressure?

Installed height is 2.00" to to outside of the retainer, but theres that second ridge on the retainer that the inner spring rides on.

I guess what my original question really was is am I better off shimming for proper seat pressure with extra open pressure, or for proper open pressure with to little seat pressure?

Do not go too little on spring pressure at either spec. If you have no other choice, at least meet the minimum spec at both ends, and go over on one if needed. So, my answer to your specific question above is, go for proper seat pressure and accept the extra open pressure. Insufficient spring pressure is not your friend.

#1. You need to check the springs with the retainer.
#2. You need to run 135-140 seat and let the open pressure fall wherever that leaves it. Don't guess!