Do you have a street demon or a road/speed demon style carb? I had a street demon carb on a 360, and didn't have very good luck with it. The metering rod steps seem have too large of a step, where I couldn't dial in the cruise/part throttle. I've had a 750 speed demon on a 440 and it ran pretty good after doing a jet change.

Tune it like a 4150 Holley

If it has a billet style vacuum pod on it, I would suspect it to be a speed demon or maybe a mighty demon (4150 styles). Either way, probably way too much carb for a mild 5.2 or 5.9. I assume it's a small Block?

When is the hesitation occurring? Off idle or when opening the secondaries (or somewhere else)? I have a Mighty Demon 850 CFM annular discharge and it was stumbling while driving as I hit the secondaries. I shut her down, popped the hood and tried manually depressing the accelerator pump on the secondaries ... there was no pump shot. I popped the secondary bowl off and inspected the billet metering block. Much to my surprise, one of the very little pipe plugs in the pump shot circuit in the metering block had fallen out. I looked in the bowl and the plug was stuck in a little bit of crud in the bottom corner. I cleaned the plug, gave it a little red loctite and screwed it back in. Hesitation problem solved!!

If the hesitation occurs off idle and it is a Mighty Demon, I would remove the carb, flip it upside down and see how much of the transfer slot is exposed in the primaries. You want about 0.025" of the slot showing. So adjust the idle set screw to get 25 thou of the slot showing. The slot exposed should almost look square. One of the great features of the Mighty Demon is the idle air bypass screw that is beneath the air cleaner hold-down stud. This is there for big displacement engines that need more air at idle and/or big cams that need higher idle RPM. With the transfer slot set correctly, use the air bypass screw to set idle speed and tune the idle mixture screws (all four) to get best idle quality.

My Mighty Demon runs great with no bog or hesitation. it's a little fat at idle but it doesn't foul the plugs. I just picked up a wideband A/F gauge from Innovative Motorsports so I can see where my mixtures are at throughout various driving conditions. I really need to get that installed to do additional carb tuning.

It looks like a speed demon, that someone painted pretty colors! Just from a quick look, it seems the throttle return spring may be interfering with the accelerator pump arm. It might not returning all the way back to it's normal resting position, and maybe not getting a full accelerator pump shot?

It looks like a speed demon, that someone painted pretty colors! Just from a quick look, it seems the throttle return spring may be interfering with the accelerator pump arm. It might not returning all the way back to it's normal resting position, and maybe not getting a full accelerator pump shot?

I have had a couple of those Demons and didn't care much for them. Took more tuning that most.

If the carb is the trouble by being too lean off-idle, then the first thing I would do is to change the power valve. It probably has a 6.5 in it now and I would put a 9.5 or 10.5 in it. Twelve bucks or so and 15 minutes is all it will take. Most auto supplies can have one the next day. 125-105 is the Holley number.

How far out are the idle mixture screws now?
Try turning them out another 1/2 turn to enrichen it, and then go drive it If it is better focus on the primary idle and transition circuits and maybe the accelerator pump tuning also, pump shot and squirter size
Off idle bogs and hesitations can be cause by to lean and or to rich also, going richer first is safer than going lean