SECONDARY LINKAGE SCREW
 

THERE IS A ADJUSTMENT SCREW ON THE SECONDARY SIDE OF MY CARB WHAT IS THIS FOR AND HOW DO I KNOW WHEN TO ADJUST IT IF NEEDED?

Are you talking about the secondary idle adjustment screw? If so it allows you to adjust the idle on a car with low vacuum/big cam, without uncovering too much transfer slot in the primaries.

Curtis

INSTEAD OF RAISEING THE IDLE WITH THE PRIMARY ADJUSTMENT SCREW I CAN RAISE IT MORE IF NEEDED WITH THE SECONDARY SCREW.
900 RPM WITH PRIMARY & 200 MORE WITH SECONDARY.

They are normally adjusted the same, if the primary is in say 4 turns, the secondary is in 4 turns also.

secondary
 

I like to take the primary to a minimum position and then adjust the secondary to get the RPM I want. I think the carb is more responsive off idle that way. Just my opinion.