A- Secondary lockout. Locks the secondary valve C- closed when the engine is cold. Opening the secondary when cold can cause hesitation, or bog. One thing seldom mentioned is that excessive engine wear can occur at high RPM on a cold engine.
How to adjust the secondary lockout?
Secondary Adjustment on Some Quadrajets
This type does not use a secondary lockout as shown above.To adjust the type of Quadrajet secondary illustrated in the photo.Open the throttle until the rod touches the lever at A.Measure the gap between the rod and lever at B.Adjust by bending the lever at B.
How to Adjust the Secondary
Secondary Throttle Valve Alignment
Remove throttle body and hold up to the light to check for any excessive clearance between the secondary throttle valves and their bores. These valves can be aligned by loosening the valve to shaft screws and repositioning the plates for tighter seals. The secondary plates are the only plates that should be adjusted. If, after adjustment, the gap is till too great, the throttle body should be replaced. A good guide in judging this would be to compare suspected throttle body with one of known good carburetor. This condition can also cause some cold start complaints in the more severe cases.