Competition Cams 54-426-11 XFIRPM Hi-Lift XR275HR-12 Camshaft for LS Gen III/IV, Three-Bolt HYDRAULIC ROLLER - XFIRPM Hi-Lift: Great street/strip camshaft for mid-range and high rpm power. Requires custom tuning. 275/277 Advertised Duration, 222/224 Duration @ .050 inch, .566 inch/.568 inch Lift, 112 Lobe Separation Use Beehive Valve Spring part #26918-16 with this camshaft