400 SB loading up

[1fine409]

I recently built a 409 (400 .040 over) for my 87 c10. I have had numerous problems with it loading up upon first start up. It still has the factory electric fuel pump in it (was throttle body before), Mallory pressure regulator regulating down to about 6 psi at the carb, Holley 770 Street Avenger carb, idled around 1,100 rpm. I usually try to turn the fuel pump and let it run off the bowls for about 10 seconds or so before i shut it off, hoping to ease the problem. I also start it up with the pump turned off, trying to help the loading up as well. Any input would be very helpful.