So with the engine timed, and sitting cold, we can adjust the carb. The air cleaner can be off for this. Plug all open vacuum ports. The two idle mixture screws on the front of the carb should be screwed in lightly, then screwed out 4 or 5 turns. This is a very rich setting for now. When you first press the gas pedal down, it closes the spring loaded choke flap. It also sets the fast idle cam on the pass side of the carb so the engine will run fast until it warms up. The choke flap closes completely and that forces extra fuel to be added. This helps the engine start and once it does, the vacuum break cracks the choke flap open a little to provide more air. That is the little plastic vacuum canister on the pass side of the carb with a hose going right into the port on the carb. There is a spec for how much it opens. Leave it alone unless the engine runs badly and then we can fix that. The fast idle cam has a screw that can be adjusted for the fast idle. You need the tachometer for this. Start the COLD engine and see what the fast idle is. Adjust it so it is around 1200 to 1500 rpm. No more than that. If it starts going way too fast, shut the engine off or it will start to warm up too soon. Adjust it down and re-start until it is right. As the engine warms up, the choke will open and the fast idle cam will drop down lowering the idle speed. But don't expect it to do that by itself. This is where you tap the gas pedal once or twice to take the screw off the cam and the idle will drop. Once at operating temp the choke will be totally open and fast idle cam will be totally released. Now the curb idle screw on the driver side is adjusted to around 700 rpm. To adjust the mixture screws you need the vacuum gauge hooked to manifold vacuum and tach. You slowly screw in each mixture screw alternately and watch the vacuum gauge. As the mixture is leaned out the vacuum will rise. The engine speed will also increase so use the tach and adjust the idle speed screw back down. Keep doing this until you get the highest vacuum reading you can, while keeping the idle speed between 650 and 800 rpm. As you get past the ideal lean setting the vacuum will drop so back the screw out until it goes back up. A healthy stock engine will show 20" or more vacuum and the needle will be steady. If you have the THERMAC air cleaner do the final fine adjustment with it in place. As stated above, the vacuum advance you choose will affect the idle characteristics. Try both ways. It is very rewarding to do this operation yourself and get the maximum smoothest possible idle.