Mandrel is machined to allow the racer 2.250" of adjustment to move the acc. drive pulley on the mandrel. There are two flats machined to give the set screw a spot to locate on and lock the pulley down once the location is picked.
Mandrel has a male register on the backside to register in the harmonic dampner. BBC register is 1.600" x .100", SBC register is 1.245" x .250". BBC crank bolt is 1/2"-20 threads, SBC crank bolt is 7/16"-20. Mandrel length from backside mount surface to front on BBC is 3.500", SBC is 3.250".
Racer can pick engine type from drop down menu.