Vetal

iTrader: (3)

All right, this is another new area for me which I'm trying to learn.
I have unknown double springs. I don't have spring micrometer, so we measured pressures assuming 1.8" spring height. That is what manual says and what I VERY ROUGHLY measured on my heads.
We got 130-138lbs pressure at 1.8"
at full lift (1.8-.624 / 1.8-.610) we got: 360-370lbs on intake and 356-366 on exhaust.
We also measured coil bind at 1.045"
that means, I have .13" "reserve" on intake and .145" on exhaust.
That means I can shim them .060 to get extra 20-25lbs seat (and full lift) pressure?

Am I understanding this whole topic correctly?

vettenuts

iTrader: (4)

First question, did you measure installed height with a spring micrometer or are you assuming they install at 1.800"? For the record, mine have installed on stock heads at approximately 1.765" height.

That aside, if you start at 1.800 inches with 130 lbs of force and then with a further 0.624 inches got 356 force, the stiffness is (356-130)/0.624 = 362 lb/inch. So if you shim another 0.060", you increase both seat and open force by 0.060 inches X 362 lb/inch = 21.7 lbs.

So it sounds like you are doing things correctly.

Vetal

iTrader: (3)

vettenuts, like I wrote, I don't have spring micrometer.
So we measured at 1.8", adding max lift from there then. If installed height would be 1.765" like yours, that's another +13lbs
Then if I shimmed .06", I would got 130-135lbs +13lbs +22lbs, which would get closer to 170lbs.
Confused

vettenuts

iTrader: (4)

Those numbers are about right, but without the spring micrometer it is hard to measure accurately since all the numbers are really based off of the installed height.

Vetal

iTrader: (3)

Now the question is, if I shim my springs to 150lbs seat / 380 open pressures, is it that bad NOT to replace my old dual springs?