Chevy Smb Double Roller Timing Set.  Application for flat tappet cam, 262-400 first generation smb engine.  Includes steel cam & crank sprockets, true double roller chain and instructions.  The cam sprocket is a 3 bolt design while the crank sprocket  is machined with three keyways--4 deg advanced, standard and 4 deg retarded.  Teaming with a  rugged true roller chain that has a solid bushing design to help eliminate chain stretch.  This set will give more  accurate timing and longer life at a good price.