Oh, now dont be bashful. 266/106 and fairly lopey?Fairly?
I new something was off...my thinking was off.
The biggest cam I ever tuned was the 292/509, which they say is 248@050. That cam I would say was fairly lopey.That was fairly simple to dial in.
Your cam,at some 18* bigger, Ima thinkin, fairly, is being modest! Ima also guessing that would be a stroker?That would be almost the only way to make it docile enough for to run it on the street.
As to the stalling while braking, I'm sure you've tried everything, but I'd like to throw a couple of things at you;
If it happens while stopped, in gear, and braking, its probably a bad booster.If you dont got one, then IDK.
If it happens while coming to a stop, I would suspect a high fuel level, and or fuel slosh, assuming the timing is close to correct, and the TC is not too tight.
Just throwing stuff atcha.
Heres a test for you.Take her out, fully warmed up, and hit the brakes to stall or nearly stall her out.(proving the issue still exists)
Next,if you have a booster, defeat it, and now repeat the test.If it still stalls, I'd go with the high float level/slosh idea. But if it doesnt stall, I suspect the booster.
I should also mention, And bear in mind I've not tuned a cam as big as yours, that there is such a thing as too much idle-timing. What I have found with too much idle-timing, is, its possible to get the t-blades too far closed, and running into a sync problem between the transfer slots and the idle discharge ports. Then when the blades slam shut on decel,under heavy braking, and the fuel stacking up on the front of the bowls, the carb goes momentarily lean,just enough to cause a stumble or a stall.The same thing can happen on a 4-corner idle carb if the secondary mixture screws are pulling a too-high share of idle fuel.
To cure this, pull the carb off and flip it over. Check the sync. The T-port should be slightly rectangular(best), to square.If its not, that could be the problem. You will want to make it so, and bolt it back on.From this point on,try to leave that curb-idle screw alone. Adjust the idle speed using other methods; such as secondary cracking, and initial timing, or an idle-air bypass circuit. Reset the idle mixture screws as may be required. This is part of how I tuned the 292 cam. It idled at 850 easy enough, and took anything I could throw at it. It had a V-can hooked to the spark-port, and it liked a ton of vacuum advance, to smooth it out off-idle and under part-throttle.Your cam is several sizes bigger,( probably around 310 to 315? advertised), so your results may vary.
I suppose you've been down this road,and I've not said anything new. If so, just ignore me. I'm just trying to help. I hate a stalled engine in traffic! More so if its flooded.