Here's something I've never run into before (800DP):
When running, Sec pump arm is locked, won't move. Pull carb off, disassemble, reassemble, works fine. Back on motor, start up, locks up again. Check ball @ pump is free, arm isn't bent. Right now with engine off, adjustment backed completely off, still locked.
Probably the 20th Holley I've been through at least; what did I miss? Carb was built up from a buddy's spare parts but otherwise seems OK.