They have an excellent level of fatigue life and are designed to handle the demands of performance engines with 585 and smaller lift camshafts. Dyno proven and track tested. Valve springs use a much smaller and lighter weight retainer which drastically reduces the valve weight creating a much quicker revving and smoother motion than comparable dual valve springs. ECONO springs allow up to 585 lift cams, no rocker box clearancing required. Eliminate valve spring separation, maximize stability, reduce valve-train noise & harmonics!Available for 5/16 and 7mm valves FEULING. Valve springs must be installed at the correct OPEN HEIGHT, matching max lift to the open height spec of the valve springs Kits include: FEULING. Valve springs, lightweight 7°steel retainers, machined heat treated chrome moly spring seats, seat shims, valve locks and a set of premium Viton. Valve seals equipped with a spring loaded valve stem wiper system. The item "Feuling Econo Beehive Valve Spring Kit 1120 Harley'84-'04 Evo Twin Cam XL Buell" is in sale since Sunday, February 23, 2020. This item is in the category "eBay Motors\Parts & Accessories\Motorcycle Parts\Engines & Engine Parts\Other Engines & Engine Parts". The seller is "sum-body1" and is located in Olmsted Falls, Ohio. This item can be shipped worldwide.