Idle Screw reaction

[saltshaker]

I Went thru this...I couldn't shut down a barrel by turning the mixture screw all the way in, so i took the tops off all the carbs removed the squirter and float. I pulled the idle jet stack out and got a can of carb cleaner and with a long straw that fit in the spray head i up it in the passage that feeds the idle circuit... There is one on each side of the fuel bowl opposite side of the exhaust jet. Squirt the cleaner in there till it starts to come up where the idle jet screws in.... Blow air back down it to finish clearing the passage. I would do all 4 carbs. To get the idle circuit working correctly I took out the main jet stack so the idle circuit would work on it's own..... The start to work on the main circuit.
My 428 was 435 ci w/ a cam 236@.50
My combo worked good for me
65/120 idle
160/175 main
F11 emulsion tubes
7/8 turns out.....
Good Luck, Jon

[PaulProe]

Figured it out - the carbs originally came with 120 main air correctors (all new 48IDA's bought in the box do) and everyone reported don't worry about the correctors, they only affect the high end of the main mix. That is incorrect!

If the air corrector is too small and you have a strong signal (vacuum), it will cause the mains to feed slightly, even at low/idle speeds. And it causes your mixture to run extremely rich. Once I opened up the air correctors to around 200, the mains & idle jets began to operate as you would expect.

As I understand it, the air correctors not only control the high end mix of the mains, they also determine when the mains begin to come on line. Too low and they are "on-line" all the time.

I'm not done yet, but I am once again moving forward. Hope my experiences will help another newbie.

Paul

[saltshaker]

Paul, Emulison tube determine when the fuel starts to enter the main circuit. The 120 is a idle jet holder for the idle curcuit and the air corrector is for the main circuit, they are a aid to either lean or richen the jet. They have nothing to do with when the fuel transfers from idle to main... That is done by the emulsion tube. If your motor is a FE then I as many others found F11 tubes to work
You can call me if you want to talk
Jon
4844109570