This hydraulic flat tappet is used on the 350-300 and 330 HP special performance engine P/N 12355345, and 12486014. The duration at lash point in degrees (intake/exhaust) is 320/324; duration at .050" tappet lift (intake/exhaust) is 212/222 and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 435/460. Valve lash is zero/zero and lobe centerline is 112.5 degrees.