493 carburetor tuning question

Zachary Egnitz said
Hello all, I am trying to tune the carburetor on my 493 stroker but I have never worked with anything this big and neither has my dad nor my co-workers so I'm hoping I can get some insight from those of you with experience. Firstly here are the specs of the motor.
Engine:
493.41 cu. in.
10.89 compression
Bore 4.35
Stroke 4.15
JE SRP pistons
Eagle crank and rods
Trick flow 240 cylinder head
Edelbrock torker 2, single pane intake manifold
Holly 850 double pumper
1.6 rockers (Harland sharp)
Crane cam duration 234/242 at .050, lift .575/.595* (689551)
Howard lifters
Eagle crank and rods
Doug 2in headers
MSD distributor with mechanical and vacuum advance.
Here's the current situation. The car runs really well, starts well even when cold. Timing is ~32° at 1000 RPM (with the distributor vacuum line disconnected) and ~53° at 3000 rpm with vacuum advance. I'm pretty sure I'm running rich because my tail pipes are black and your eyes burn if you run it in the garage for more than a minute (even with the doors open). My fuel bowls are where they should be (right beneath the center line of the sight window). Here's where I get confused. When I tried setting my idle mixture screws I turned them in all the way and then slowly brought them out one half turn at a time until I got the highest rpm. However, the highest rpm occurs when they are screwed in all the way. When I unscrew them the rpm goes down. This led me to believe jets were too big however with the screws all the way in the engine bogs when i hit the throttle quickly. I took the screws out half a turn and the bog is less significant. I took them out another half turn and the bog is basically non exsitant and the car pulls well. Right now I have them 1.25 turns out and the secondaries are 1.5 turns out I believe and the car runs great, good throttle response, pulls well and doesn't bog.
To reiterate, I don't have much experience with engines this big but I find it odd that my rpms go down when I bring the screws out and my tail pipes are black but if I bring the screws in it bogs and looses power. Is this just normal for this size engine with the cam I have? Should I just keep it how it is? Should I put smaller jets in? Any input would be appreciated :)

Mattax has you going in the right direction. When tuning any carb for the first time always get brand new plugs it in first, then get your timing at idle correct and you would want something in the low 20*s without vac advance with that cam imo. Then get the total set at about 35* without vac advance. Then get the tune on the mix screws and they with end up some where between 1-2 full turns out and all 4 should be exactly the same turns out. The idle blade screw will be about 1.5 turns out to get the t-slot exposed, you will have to take the the carb off and check. Adjust both pri and secondary t-slot with .020 exposure. If your mix screws need to be less than 1 turn out you will need to change the IFR to a smaller one. If the mix screws are not out enough you will have a stumble because these screws initialize the fuel transfer when you crack the throttle. Check your plugs for how its burning. should be fairly clean on the base circle on the shell of the plug and the ground strap should show the burn to the bend of the strap, if its burned to the weld its too much timing and if its on the tip not enough, on the bend is just right. Others things can influence that as well like different fuel as the ground strap is a heat indicator, but is does help to get timing close. Yes, also make sure the float level is in the middle of the glass with the new holleys and at the bottom if you have the brass plugs before you start. Hope this helps