Jayman;

First of all, do not enlarge the jets.

The Quadra-bog carbs were designed to richen the mixture as the vacuum signal decreases. Similarly to that of the Holley carbs which use a power valve. This is done for the sake of fuel economy.

When you install a larger duration cam than stock, the vacuum signal goes south, tricking the carb into thinking it is under load, as in acceleration mode. This in turn opens the power valve or boost valve and richens the fuel mixture by 6-8 sizes. Now when this occurs during idle, just think of the fuel ratio in the engine.

Well it gets worse. The first thing the hot rodder does is turn the idle screw clock wise to try and compensate for the motor wanting to stall. As you do this, the butterflies open a slight bit more, which in turn signals to the carb to dump yet more fuel into the venturies. To make a long story short, you have a horrible running motor which is inefficient and doesn’t make near the power that it should.

The reason your motor idles alright for a bit is because you have cleared the chambers by revving it however as you come to an idle, the motor richens up and slowly floods itself. The other problem you have is that your vacuum advance becomes non-existent at idle with a big cam and therefore the engine idles at 10 degrees rather than 30 plus.

Is this all makes sense so far, please acknowledge and I will tell you step by step what needs to be done.