Intake Installation

Sorry....440, massaged 915's, Edelbrock RPM, 770 SA Holley, Low pressure/high volume oil pump, 400 HP/550 torque, all stuffed into a 69 Barracuda notch.
Well, yanked the carb/intake off and this pic shows what i found....cracked valley pan. Its in the middle of the pan just a couple of inches off centre towards the back. Its weird, as this engine only has 600 miles on it and the pan was new on the rebuild.
It explains my oil leak for sure. I'll get a new pan with the riser blocked off already, re-install and hope for the best.
Any ideas what would crack a new valley pan?