Fits Aftermarket Blocks With .400 In. Raised Cam. Suit Bb Chev. Lose Oil Pressure And The Engine Is Trash. Now You Do Not Have To Depend On A Stock Oil Pump Drive Shaft In Your Expensive High Performance Or Wet Sump Racing Engine. Arp Oil Pump Drive Shafts Are Made From Heat Treated Premium Aerospace Chrome Moly. We Have Increased The Body Diameter To Make It Tougher - More Able To Handle The Added Torque Requirements Of Increased Capacity Oil Pumps Or Heavy Viscosity Racing Lubricants. Rated At 170000Psi The Added Tensile Strength Delivers Longer Service Life Of This Critical Component.