# Rochester 2GV Idle Air Screw NOT Idle Adj Needles



## GtoFM (Mar 23, 2018)

'66 389 Tripower, Center carb (7036175) with hot idle compensator within the float bowl section. On the back exterior, directly below the compensator location is the 'Idle Air Screw (for by-pass idle systems)', as described in an old rebuild sheet. The screw appears to regulate air to a channel underneath the venturi cluster where it connects both idle passages leading down to the idle adj needles. 
My problem is the Idle Air Screw only moves 1/4 turn. I have searched this and other forums as well as the internet for its function and adjustment but no luck. The old rebuild sheet suggests backed out 2 turns from seated but nothing on fine tuning. The engine is not assembled.
I understand the function of the hot idle compensator, which is regulated by temperature, but not clear on the function of the idle air screw which is adjusted manually. It has been suggested it was a failed attempt to improve idle and is not needed, but that is just a theory. Looking for a better explanation.

THANKS


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