spring pressure calculation for different heights
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spring pressure calculation for different heights So I'm chasing some possible valve float.
I'm running an xer lobe 236/232 .595 .600 on a 115lsa with prc dual springs rated for max .675 lift. Also have yella terra 1.7 rockers.
I had a shop set the heads up a couple years ago. Its running between 10 and 20 psi boost and made 870whp. Only thing is its done at 5200rpm.
The prc springs are around 145 seat pressure at 1.810 installed height. Im going to check the height tomorrow. If they are indeed at that height im going to need about another 40psi seat pressure.
How can i figure out what installed height i need for 180 to 190 seat pressure?
Thanks
Alex
I'm running an xer lobe 236/232 .595 .600 on a 115lsa with prc dual springs rated for max .675 lift. Also have yella terra 1.7 rockers.
I had a shop set the heads up a couple years ago. Its running between 10 and 20 psi boost and made 870whp. Only thing is its done at 5200rpm.
The prc springs are around 145 seat pressure at 1.810 installed height. Im going to check the height tomorrow. If they are indeed at that height im going to need about another 40psi seat pressure.
How can i figure out what installed height i need for 180 to 190 seat pressure?
Thanks
Alex
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Joined: Apr 2002
Posts: 6,080
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From: So.Cal.
+1 what KCS said.
spring’s at at-rest height = L
at 1.1810” height, force is 145 lb
deflection from at-rest height = x = L-1.810”
Hooke’s Law:
F = k.x
your current setup 145 lb:
145 = k.(L-1.810)
for 180 lbs:
180 = k.x
then solving both equations:
180/145 = (k.x)/(k.(L-1.810) = x/(L-1.810)
so x = 180/145 * (L-1.810)
you need to measure the at-rest height L;
installed height will be L-x.
Similarly, for 190 lbs:
x = 190/145 * (L-1.180)
installed height will be L-x.
spring’s at at-rest height = L
at 1.1810” height, force is 145 lb
deflection from at-rest height = x = L-1.810”
Hooke’s Law:
F = k.x
your current setup 145 lb:
145 = k.(L-1.810)
for 180 lbs:
180 = k.x
then solving both equations:
180/145 = (k.x)/(k.(L-1.810) = x/(L-1.810)
so x = 180/145 * (L-1.810)
you need to measure the at-rest height L;
installed height will be L-x.
Similarly, for 190 lbs:
x = 190/145 * (L-1.180)
installed height will be L-x.
Not sure what heads you have, but I have never had GM heads with stock valves set up that high. They are more typically at 1.765" installed height.
Also, if you crank the seat force to 185, careful of the over the nose spring force as you may just kill the Yella Terra rockers in the process.
Also, if you crank the seat force to 185, careful of the over the nose spring force as you may just kill the Yella Terra rockers in the process.
Maybe your springs are tired?
This is how I set mine up for .631 lift
.631 lift + .050 (clearance) = .681 + the springs coil bind, which is 1.070 = 1.751 so my springs are installed (shimmed) at 1.750 respectively.
This is how I set mine up for .631 lift
.631 lift + .050 (clearance) = .681 + the springs coil bind, which is 1.070 = 1.751 so my springs are installed (shimmed) at 1.750 respectively.
