My name is mike miller NAM VET 1968-69 Thank you for answering my question. I have a 70-1970 7045214yb 1536 gm motors rochester Quadra jet There are 2 two mixture screws at the base looking at the front 1 one under the fuel filter and the second one on the right of it, which one is the fuel mix and which one is the air mix THANX MM

The air/fuel mixture screws meter the fuel that flows under each primary throttle plate when the throttle is closed at engine idle. Both of the air/fuel mixture screws control fuel flow.

Turning the mixture screws "in" will decrease the fuel flow and "lean" out the air/fuel mixture, and turning the mixture screws "out" will increase the fuel flow and "en-rich" the air/fuel mixture.

To adjust the air/fuel mixture warm up the engine to normal operating temperature and with the choke off at normal idle speed. Adjust the air/fuel mixture screws one at a time, and turn each air/fuel mixture screw "in" until the engine just begins to mis-fire, then back the air/fuel mixture screw "out" 1-1/2 - 2 turns a half turn at a time until the idle is smooth.

If you need a base setting to start with, then turn both air/fuel mixture screws "in" until they lightly seat, and then back them "out" 1-1/2 - 2 turns and then start and warm up the engine and then proceed to adjust the air/fuel mixture as described above.



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