The tech really isn't all that different, the CFM is for sure. After I had it all dialed in right today, it was pulling pretty good. And with no bog it would likely be a close race. I think having a carb that runs w/o a bog is better overall since you won't have that letdown in sensation.

I went out and found an old FSM and it says subnormal engine heat will cause a lean condition. So that would support the theory that the cooler air has something to do with the big drop in performance.

So that leaves two things I can do-

1. Richen up the carb.
I could swap to AFB Eddy jets/rods if I can find my strip kit.
I could drill out one of the two other sets of jets. That would require buying a small drill set, maybe a pin vise.

2. Change to a hotter stat. I looked and i have a 180 Robertshaw and a 190 that looks to be a Robertshaw that isn't stamped by them. Definitly a high flow unit. I have had these on the shelf for years. I also have a gasket.

Problem with option 2 is that I really like that my engine runs as cool as it does. I know that I might be seeing some increased wear, but the comfort in knowing that gauge has never, ever went past 180 makes for some serious piece of mind when driving. I bet that it would hold whatever temp the stat I would put in but still.

I'm headed out of town for a few days so I will have time to weight it out. I really need now to drive it on another hot day to get it up to 180 again and see if that will cure it. i sure don't want to change stuff on a goose chase. I just can't see any reason why it would be anything else.

One long shot could be the plugs got fouled when i was checking the WOT. I drove around quite a bit and beat on it so I think that would rule that out.????

A few other notes-

Could the Eddy have had the bog from being too cold as well?

The AVS doesn't start as fast as the Eddy does. The Eddy usually was running so fast that you couldn't hear the starter. Really. The AVS starts right off but i would say it takes a full second longer. That isn't a problem but I found that interesting.

I've been running a 3/8 "rebuild kit" spacer under both of them sandwiched between two gaskets. The Eddy seemed to like it and I can't run anything that is thicker. Never had a hot start problem with either carb. Eddy was fine hot starting w/o the spacer. Never tried the AVS w/o it.

This thread is the third thing to pop up on a Google search on AVS tuning.

Update-

The 190 stat helped but still not got it right.

The accel pump went bad, based on popping on tip in occasionally.

Put new pump in and checked the pump shot adjustment and figured out that I hadn't backed the idle screw off the last time. The adjustment was off.

I took an arm off a parts carb and bent it to work. I have the other to use as a baseline if needed for some reason.

Still not running right. Got back home and looked at the shooter yet again. Noticed this time that every so many pumps results in the fuel coming out from under the gasket. Guess I will put another new one in.

Hope this gets it. Getting sick of taking the carb off and can't take the hurt back to lean over the fender. Probably bend it if I did anyway.

I pulled the carb again and changed the shooter gasket.

Still have fuel seeming to spill out from under the shooter.

I doubled up the old gasket with the new and still had the same problem. So I took a light and closely watched as I ran the pump. The fuel I'm seeing is actually a "drip edge" like effect where it is curling back up the bottom of the shooter nozzle and then spilling out on the bore of the carb.

So is this normal? I'm about at my wits end on this one. If I solve the off idle stumble I should have a pretty decent carb all around.

Maybe I need to drill out one of the parts shooters? Maybe fill one and drill a smaller hole to cause it to shoot out with more PSI, but that maybe in turn cause a volume issue.

850 seems like a really high idle for a stock 383 Magnum.

I like AFB's and AVS's. I am planning on rebuilding a 340 Buick AFB for a slant.

I went with a shooter out of the 69 383 AVS. Really no change. This is a hit or miss problem. If you give it enough gas taking off you are fine, still even with the new pump it pops on hard throttle sometimes.

The idle is more like 750 right now. No change. At 800 it is still on the idle circuit. One chart i had called for it to idle that high anyway with a stick trans. Not sure it really matters.

I can still go with the top hole "big shot" and see if that cures it. Could try a pump with the neoprene(sp) seal instead of the leather.

This has been both a fun and frustrating deal. The carb works 90% of what I would want.