Trick Flow Specialties TFS-16918-16 - Trick Flow® by PAC Racing Beehive Valve SpringsTrick Flow by PAC Racing Beehive Valve Springs Valve springs compress and rebound hundreds of times a second. Make sure your next set of valve springs are built to lastand built to win! Trick Flow by PAC Racing beehive valve springs allow you to drop in a more aggressive cam without machining your spring seats (most applications). PAC springs are CNC coiled from high tensile strength, extra durable Pacaloy chrome silicon steel and double shot peened