Thread: 400 sb chevy and carb

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i have a 406 small block chevy....with 850 holley whats the best way to adjust the carb.. is there a standard for the air screws...should i adjust timimg first then go to carb..thanks.....any help appreciated.. like turning the screws all the way in and leaning them out a couple turns whats best?

Best way is to use a vacuum gauge. Set the timing where you want it first. Then set your idle speed where you want it. Connect your vacuum gauge to manifold vacuum. Then adjust each idle mixture screw to achieve maximum vacuum, then back it out 1/4-1/2 turn richer. Usually I will start by turning the screw in till the motor stumbles, then back it out till the max vacuum is achieved. After the first screw reset your idle speed if necessary, then adjust the second one. After it is all done, reset your idle speed if needed. If you don't have a vacuum gauge a tach will also work. Instead of max vacuum, you want max RPM(without moving the throttle).

Pat