Valve Spring Rate Calculator

Inputs

View results
Measured wire diameter of the valve spring.
in
Mean coil diameter, usually outside diameter minus one wire diameter.
in
Coils that deflect under load.
Total wire turns used for the solid-height estimate.
Uncompressed spring length.
in
Spring height at the valve-seat condition.
in
Net valve lift at the spring.
in
Minimum open-height clearance to solid height used for the badge verdict.
in
Sets shear modulus and the static stress screening value.

Results

Default result
Edit inputs
Spring rate(k)
166.5lbf/in
Pass

Helical spring rate k = G*d^4/(8*D^3*N_a).

Also computed

Seat load(F_seat)74.95lbf

74.95 lbf

Load at installed height, from free-length compression only.

Open load(F_open)Caution158.2lbf

158.2 lbf

Load at installed height plus entered valve lift.

Coil-bind clearance(C_bind)Pass0.166in

Open height stays above estimated solid height by at least the entered target.

Open-stress utilization(U_tau)Caution99.75%

Wahl-corrected open stress divided by the material screening allowable.

Open corrected stress(tau_open)122.6ksi

Wahl-corrected torsional shear stress at open lift.

Allowable shear stress(tau_allow)122.9ksi

Screening allowable from Chrome silicon spring-wire data.

Spring load vs Valve lift from seatLoad line from seat to open lift using the calculated spring rate and installed-height preload.Spring load vs Valve lift from seat05010015020000.20.40.6openValve lift from seat (in)Spring load (lbf)
Load line from seat to open lift using the calculated spring rate and installed-height preload.
Valve spring preview COIL-BIND CLEARANCE OPEN-STRESS UTILIZATION 704 N open load 4.2 mm bind clearance
Method notes 2 notes
  • This is a static geometry screen for a linear helical spring; it does not model cam dynamics, surge frequency, installed preload scatter, retainer-to-seal clearance, guide clearance or fatigue life.
  • Use measured spring data or manufacturer seat/open load specs for final engine assembly decisions.

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