Every camshaft profile is built around an assumption about spring pressure. When the actual valve spring installed does not match what the cam designer expected, the engine can lose power, float valves at high RPM, or wear out the valvetrain long before it should. Understanding spring pressure is one of the most overlooked steps in building a performance valvetrain.
Seat pressure is the load the spring applies when the valve is fully closed. It exists to keep the valve seated against combustion pressure and to prevent valve float at idle and low RPM.
Open pressure is the load at maximum lift, when the spring is compressed the farthest. This number controls how well the spring can control the valve and follower as lift and velocity increase through the middle and top of the RPM range.
If spring pressure is too low for the camshaft’s lift and lobe acceleration, the valve can separate from the lifter or rocker at high RPM. This is valve float, and it costs power immediately and can lead to contact between the piston and valve.
Excess pressure beyond what the cam needs adds unnecessary load to the lobe, lifter, pushrod, and rocker trunnion. That extra friction accelerates wear, increases parasitic drag, and can actually cost power rather than add it.
Start with the camshaft manufacturer’s recommended spring pressure specification, which is calculated from the lobe’s lift, duration, and acceleration rate. From there, factor in your redline. A cam intended for a 6,500 RPM street engine needs less open pressure than the same lift used in an 8,000 RPM race combination, because higher engine speed increases the inertia the spring has to overcome. Coil bind clearance also has to be checked at maximum lift, since a spring that is compressed solid before the cam reaches full lift will bend a pushrod or break a valvetrain component almost immediately.
Single springs are simple and lightweight, well suited to milder street cams where seat and open pressure requirements stay modest.
A dual spring setup uses an inner and outer coil to add pressure capacity for higher lift, more aggressive cam profiles without the coil bind issues a single spring of that pressure would face.
Beehive springs taper toward the top, which reduces reciprocating mass at the retainer and allows for higher RPM control without the added weight of a full dual spring setup.
Because seat pressure, open pressure, coil bind height, and installed height all have to work together, guessing at a spring rarely ends well. Liberty Performance Parts carries single, dual, and beehive valve springs built for street and racing applications, which makes it easier to match a spring family to the pressure your specific camshaft calls for rather than forcing a compromise. Checking installed height and coil bind clearance before final assembly is still essential, but starting from a spring designed for performance use puts the rest of the valvetrain in a much better position to survive.
