Aftermarket cams increase the efficiency of your head by using higher lift and duration. Any time you increase the lift and duration of a cam, you are putting more stress on the valvesprings and retainers. Factory valvesprings were not made to handle the abuse of higher lift and duration, especially not at the rpm we take our engines to when racing, or even driving enthusiastically. If you are installing upgraded cams, do yourself a favor and install valvesprings and retainers while you're in there.
Your stock valve springs can fail in 3 different ways.
They can "bind" and get stuck, losing their ability to open and close the valve. This is an easily diagnosable failure. Depending on how it binds, it could cause failure to other engine parts.
They can "break" into pieces dropping the valve into the combustion chamber and consequently ruining your bottom end.
"Valve Float" is a hard to diagnose condition where the valve spring rate is not high enough to fully extend the spring and close the valve after a complete rotation of the cam before the cam comes back around again. So what ends up happening is that when the cam is spinning fast (high rpm) the valve never closes, and combustion leaks out of the engine, and the engine loses power.
B18A / B18B VALVE SPRING & RETAINER KITS
Designed for high rpm, BC valve springs by PAC Racing are wound from only the highest grade, super clean, chrome silicone alloy and feature proprietary processing procedures for consistent pressures. BC titanium retainers are CNC machined from 6AL4V round bar titanium to exacting tolerances.