Did you know small-block Ford cam thrust plates install properly only one way? And did you know the 351C, 351M, and 400M take a different cam thrust plate than 221-351W? We have found 351C cam thrust plates installed on 289/302/351W engines, and we have seen them installed backwards. When you install this cam thrust plate backwards, you're robbing the cam sprocket of important lubrication even though return oil lubricates. The slot gets oil from the galley to the cam sprocket. When installing this cam thrust plate, use a thread locker and torque the bolts to 9-12 ft-lb. Do not overtorque.