You might need more base timing. I've had that particular problem myself, and spent way too much time chasing "feul" problems. I talked to my uncle, who used to race a 235 powered '49 Chevy sedan back in the '50s, about it, he said it needed the timing bumped up. I went 15 degrees, runs great now. Mine does not have a vacuum advance, so you might need to work with it a bit to see what yours really needs to run at.
