Holley Idler Pulley 97-153 | Idler Pulley, Grooved, 59mm DI. 59 mm grooved Pulley for use with all Holley passenger side LS accessory drive brackets (this Pulley is required for LS bracket application using the standard belt spacing AND using a stock LS3/LS7 throttle body, you must replace the grooved idler Pulley with this 59 mm Pulley to allow safe belt clearance to the throttle body).