Does anyone know how much a difference the internal idle screw makes? like 1/2 turn equals___ rpm increase? it is idling well at about 650rpm but alternator output is greatly increased by even upping it 75rpm. i know the external adjustment will increase the rpm but not correctly. by adjusting the internal governor to say 750 rpm, it will keep it at 750 weather i have the a/c on, alternator loaded down in gear or nothing on in park.

__________________
83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect