The Melling SPD-31 is a flat tappet hydraulic camshaft designed for BB Chrysler 4BC engines. With an intake duration of 213 @ .050" and an exhaust duration of 225 @ .050", it has an advertised duration of 302 on the intake and 324 on the exhaust. The camshaft has a lobe separation angle of 115 and an exhaust center line of 115. It has a lift of 0.447 on the intake and 0.459 on the exhaust. The camshaft is made of flame-hardened casting and weighs 9.7 lb.