Well my issues were with the vacuum secondary . I had a 750 on mine . had a flat spot at 3000 to 3600 give or take .I tried to play with different springs but I wasn't happy. decided to rebuilt my 4781 850 dbl pump . that I had from my 512 rb .after talking with rat and vette here thought . give it a try.
well the difference is very very noticeable. The motor loves the carb . so much for fuel economy .
still have to do some adjusting on the first shot I have a bog then it grabs. The flat spot is about half a second . Feels like its flooding then it goes like a banchee!
Maybe a pooling issue or maybe the shot from the secondary is too early ?