Reply to "Holly ultra issues"

I experienced similar issues with a single plane but I was having cooling issues as well so the engine would get very heatsoaked and fuel was probably boiling over the vents. I would also experience a dieseling effect occasionally after I switched from a Holley 750 to a bigger carb. I was able to adjust that out.

My theory is the direct shot to the intake with the single plane causes more pronounced flooding. When the engine is cold the fuel does not vaporize as efficiently as it does when the engine is warm or even heatsoaked after running. So inherently you toss a bunch of fuel into the car when cold and then when its hot its just too much fuel vaporizing. One method is to just hold the accelerator pedal 1/3 of the way down, just enough to not engage the accelerator pump in the carb which will prevent flooding the chambers further. It takes a little practice but you will find the sweet spot. Another possible fix is to adjust the float/fuel level to reduce boilover.

http://forums.holley.com/entry...r-Barrel-Carburetors

As far as the slugginess at low rpm, part of that is the lower velocity created for the air now having a shorter/larger path to the intake valve, so atomization of fuel is decreased and can drop out of suspension. A carburetor with annular boosters (Holley HP) vs the (Holley Ultra) which has downleg boosters would improve atomization coming from the carburetor. This would improve low rpm throttle response, especially if you are experiencing hesitation on abrupt throttle changes.

I ran a Race Demon with annular boosters vs my Holley 750 and was pleased with the 4 corner idle adjust-ability as well. I later sold it to a member here after I switched to EFI. I'm a little more versed in EFI and you have more control over hot/cold starting fuel depending on the system. Hopefully someone else can chime in who can provide some other carburetor tweaks.