Question...I have a 71 Nova SS with a roller 355, BG speed demon 750 carb with mechanical secondaries, a 1'' spacer, airgap intake, lunati 290/290 555/555 roller cam, steel heads with 160 on the valves, MSD ignition, Taylor 8.5mm wires, 10.5 compression and other good quality goodies hooked up to an ATI 3400 stall housed in a well built THM350 rolling into a posi rear with 3.73 gears.  Enough of that, I run a combination of 93 octane and 110 Cam 2 in it.  Timing is set at 37 degrees.  The car runs great...but many times when its warmed up and I have cleared the carb out, put it in 1st gear or drive and you wack the throttle, it will hesitate instead of it going nuts out of the hole unless if I were to power brake it.  I have been told that Barry Grant speed demon carbs are tempermental and we have changed the jets some from 83 to 79.  I am not much on carbs...but what direction do I go and what do I do to clear this up.  I have even been told that the squirters or something should just roll out causing it not to bog out or get too much fuel at one time.  Otherwise, she screams like a scalded dog! Suggestions?  

Well it might be the accelerator pumps.... If the accelerator pumps do not push in the initial squirt that goes from idle rpm to full throttle than it will hesitate and then when the main jets get the fuel from the fuel bowls then your car takes off. If it is not that than I would say take off the 1" spacer between the intake manifold and carb because that extra one inch might be causing the hesitation since you probably only have about what 14 or 15 vacuum psi? What about the mixture? If you are running too lean or too rich you could bog down at the start and then pick up after a sec or 2.  

Back when I was 16 I had a 71 Ford Torino with a 302 and I had a major hesitation problem and nobody could figure out what was wrong with it. It turns out the problem was the mixture screws were just screwed out too far. I just happened to accidentally fix the problem one day when I decided to check my mixture screw adjustment using a vacuum guage. It was the strangest thing. Nobody ever thought of something so simple like that. it ran soo good after that.  

I had a major hesitation problem and nobody could figure out what was wrong with it. It turns out the problem was the mixture screws were just screwed out too far. I just happened to accidentally fix the problem one day when I decided to check my mixture screw adjustment using a vacuum guage. It was the strangest thing. Nobody ever thought of something so simple like that. it ran soo good after that.