The issue with stock springs is they tend to cause valve float as you increase engine output. Valve float occurs when the valve springs are incapable of holding the valve train against the camshaft lobe after peak lift. This happens when either the weight of the combined valve train components or the rpm speed of the engine creates so much inertia that the spring is no longer able to control the valve. The most common response to valve float is to increase the strength of the spring so that it can better control valve motion. But stronger springs generally weigh more and cause their own problems. Achieving the optimum strength-to-weight ratio is a delicate balancing act for every engine builder. The Brian Crower Single Spring/Titanium Retainer Kit is the perfect addition for those of you planning to build your head while also reducing weight, thus giving you the ability to rev much higher with less diminishing returns.