math class needed on valve springs

[FireSale]

What's the application here? It doesn't really make sense to talk pressures when we don't know what is being asked of the engine. I run PAC 1427 springs - conical for a BBC - in a SBF with NASCAR type iron heads. Stuff gets mixed up when all you want is GO...


Note: A PAC 1409x at 1.8 will give you pressures of 175/384. I'd give up on a 1.78 IS, it's too hard to shim to. 1.8 or 1.85 are common.


Note 2: What is the seat size?


Ask questions and give info. I didn't so I have 4 sets of springs now............

[Eman]

Originally Posted by gmonde

what is the math formula for a known spring rate to calculate seat and open pressure ?

spring rate is 370lbs @ 1.00"

closed valve spring installed heigh1.780
open valve spring height 2.237

seat pressure ?
open pressure ?

thanks in advance

Is the spring rate 370lbs per inch? Is the installed height 1.780? Open height can't be more than closed, what is the free height of the spring?

[gmonde]

Originally Posted by Eman

Is the spring rate 370lbs per inch? Is the installed height 1.780? Open height can't be more than closed, what is the free height of the spring?

this is the spring I am using ,I have a installed height of 1.780 and shooting for a 170 lbs seat pressure with a close to 400lbs open ,the .100 difference should get me there but, I cannot remember the formula that will get me that number ,, its been 5 years since I built the car and my info was given to the previous owners,,
I cant remember for the life of me ,, internet search is coming up short

my lift on the cam is .457

installed Height (in):
1.880 in.
Seat Pressure at Installed Height (lbs):
155 lbs.
Open Height (in):
1.280 in.
Open Pressure (lbs):
377 lbs

[pmrphil]

Garret -
If you go down .050 (to 1.830) you should have 173 seat, but your open pressure will only be a bit over 340. The 377 is at .600 lift. I believe you will need different springs.
Phil

[FireSale]

Your spring info matches the PAC 1220 beehive spring. Is it this type of spring? It sounds like you want to change the rate and pressures of a spring you have to a spring you want and I don't think it works that way. You can change the seat and open pressures by changing the installed height but the spring rate is dialed into the spring in the manufacturing process. This spring installed at 1.780 with a .457 lift would give pressures of 192 and 362. You can tweak out the IS until you have a seat pressure of 170, but the open pressure will move in the same relationship that 192 is to 362. That's the spring rate doing that.

[gmonde]

Originally Posted by FireSale

Your spring info matches the PAC 1220 beehive spring. Is it this type of spring? It sounds like you want to change the rate and pressures of a spring you have to a spring you want and I don't think it works that way. You can change the seat and open pressures by changing the installed height but the spring rate is dialed into the spring in the manufacturing process. This spring installed at 1.780 with a .457 lift would give pressures of 192 and 362. You can tweak out the IS until you have a seat pressure of 170, but the open pressure will move in the same relationship that 192 is to 362. That's the spring rate doing that.

yes,,actually the current spring I run now is Lunati 74820-16 - Lunati Pacaloy Valve Springs that matches the PAC springs,,just getting my numbers so I can check them ,they have been in the car for a couple of seasons

I checked the pressure before I installed them and they where around 170-180 @ 1.780 installed spring height,




the PAC 1220x spring is the next option but it will have to much spring pressure
Installed Height (in):
1.900 in.
Seat Pressure at Installed Height (lbs):
160 lbs.
Open Height (in):
1.250 in.
Open Pressure (lbs):
400 lbs.

thanks for the reply's ,much appreciated !