Chevrolet 262-400 c.i. 8 cyl. 1955-1998. Hydraulic-Great for Street Machines. Needs stall, headers & gears. Rough idle. Magnum Hydraulic Flat Tappet Camshafts. Chevy Magnum, 280H Great for Street Machines, Rough Idle / Valve Lift - Int(.480) Exh(.480) / Dur - Int(280) Exh(280).