Edelbrock 800cfm AVS2

Rich at idle? Shouldn't the idle mixture screws take care of that as long as the carb is working properly and the fuel pressure isn't blowing fuel past the needle and seat? I can see a little extra initial timing might help with that.
Not necessarily with a metering rod carburetor. If there's a lumpy cam with a low vacuum signal, the metering rod springs will be too strong and put the metering rods in their rich sections at idle. That's why tuning these type carburetors with a vacuum gauge is so important. You install a spring rated at an hg reading lower than what your idle vacuum reading is. Like on Gladys, she has 6hg at idle and bounces around a little because of the erratic idle of the cam, so I chose the 4hg springs and that keeps the metering rods on the lean step at idle. As soon as vacuum drops under 4hg, they get into the rich step for enrichment.