When I turn my idle mixture screws, I watch the Air/Fuel guage to assess what effects each 1/8 turn has. It is odd that you can turn almost a full turn and see so little change but then all hell breaks loose sometimes at only the tiniest adjustment.

2,000 and up probably means you are already on the main circuit. That would seem to indicate that the issue is with the idle and low speed transition. I'm thinking the slot needs more fuel.

That is, IF, the issue is carb related.

What happens if you drop it in gear(assuming auto trans?)and do a little brake stand?(that will load the ignition system)If it pops or misses then,I would lean towards plugs,coil,etc, I thought I saw/heard a miss on your video. You could also try misting some water on the dist/wires/etc and then load it down and look for fireworks.I know you said the wires and stuff were new but you didn't mention plugs. Just some thoughts, Good luck!

Well back to the 31 Shooter and got the car all warmed up to temp and put the vacuum gauge on it.

Was bumping between 9-10" for the most part reset the idle mixture screws and now it holds more steady at 10".

A quick throttle stab will still result in a pop -I nead ear plugs gonna go deaf if I don't solve this!-

I also tried running the idle mixture screws way out and with no change.

Going to look at the power valve next. Engine was too hot and I was too frustrated. Fuel injection sure sounds nice right now.

I like that you keep at it. Giving up and admitting defeat really sucks! I have been dealing with various obstacles over the years and sometimes stuff just seems UNfixable.
Did I read that you have tried different carburetors that had the same result?

Give it all the total it can take loose the vac advance if set that way and get at least a180 stat in there to heat it upI think you are fighting yourself by ear tuning it in garage wait until you can drive it and really heat it up

I already run a 180 t-stat.

The Edelbrock once set didn't pop bak at me just have what I think was some form of internal fuel leakage.

So I haven't tried any other carbs but I keep looking at the 750 Street Demon just don't know anyone running one on a big block.

The Street Demon will be the next carb on my Barracuda. And it will replace the 3310 that is on there now.

I'm running the 383 big block with some modifications. However, my 3310 needed to be really richened up to take a stumble out of it. Try this: Go to the biggest shooter and the green or blue accelerator pump cam and see if it goes away. It may run too rich, but what the hay. Then at least you'll know if it's the carb being lean. Work backward from there if the "pop" is gone. Summery: Biggest shooter, fastest shooting accelerator cam and 18 degrees timing. Don't forget to look for vacuum leaks. If that doesn't help, wont that at least tell you it isn't the carb? Just saying.

Tried an 8.5 power valve as it's what I had. Still backfired through the carb but not as easily or often.

Again only on a quick throttle stab. Also bumped the timing up to 18 initial with no help.

Pulled the 8.5 power valve and went with the "Holley Reccomended" 4.5 -as per Holley as I pull 10" of vacuum. Obviously this made it worse.

Pulling the power valve I noticed a few beads of what I think might very well be water on the metering block. -What else would make bead droplets?- Starting to think I have some condensation in the tank from winter storage. The tank is down around 1/8 so going to get some methyl hydrate and fresh fuel and try again.

I also tried the edelbrock again. The car ran horrible even at an idle compared to the 3310. Much more shake and it had a stumble to bring the rpm up slowly no matter the accelerator pump position. Still had backfiring through the carb which is why I am really thinking I may have water in the tank.

I somehow got water in the tank of my 74 FrankenDuster several years ago, The car would run but bog and stall when I leaned on it. It never backfired. I drained the tank and what came out sorta looked like Italian salad dressing!

My dad remembers working on a 440 motorhome years ago that had water in the fuel. He said it was backfiring so bad when they had the dog house off he was worried it was going to burn the interior down.

It's worth a try anyways. Can't find any vacuum leaks. Runs great otherwise no noises no misses no surging idle and can hold high rpm without missing a beat. It's doing this on 2 different carbs.

I have all new wires, new distributor as well. Waiting for my Rev-n-ator and then it will also get a new MSD coil so running out of options otherwise.

Have you actually had the chance to drive the car so that the engine could be put under load since the popping has come up? If a cylinder was partly fouled, freewheeling the engine may not clear it.

Maybe try a new set of plugs when you can drive the car. I have had a fouled cylinder back fire when revved, but would idle okay.

I would put a faster (bigger) accelerator pump cam on it and 37 squirters. also put at least a 7.5 power valve in your cam is small and 4.5 is for huge low vacuum cams. make sure accelerator pump is adjusted correctly so it provides a shot of fuel as soon as possible!

New ethonal fuels need lots of stable when car is sitting they draw water like crazy.

Jetting stock is usually good if 72's you can try 74 but no larger.

Your problem is the transition from the idle circuit to the high speed. causing a monentary lean condition before the jets take over.
The power valve is one of the things designed to help that. as you quickly open the throttle vacuum drops and the power valve opens allowing extra fuel in to help in that transition as do the accelerator squirters. the lower the number of the power valve the later it opens. pop. your vacuum sneaking up on the throttle with that mild cam my be way up to 14 or more!
So you need a little more fuel quicker the power valves and accelerator pump is the way to get it. you could slow down advance curve a smidge (slightly heavier springs) as long as you get 35 to 38 total (vacuum advance unhooked) by 3200 or so maybe even run less initial depending on the amount of advance in the distributor.

No chance of driving it until late April early May -snow sucks-

I did have a 35 shooter on it as one of the first changes with no help.

I am going to swap the 8.5 power valve back in as it did seem to have a nicer curb idle and the back firing was far less. I've never tried driving it with vacuum gauge on it but may have to make a point of it this summer.

Never played with accel pump cams before. There have been a few recommendations on what to try just haven't picked one.

Over the road my make things different as load slows down the free reving!