1966 289 3-speed
Thank you for this. Seems like I've gotten some conflicting info.Yes, it must close fully or you’ll have erratic function at best. It’s the only repeatable position to set it to. The spec in the shop manual that you use the drill bit to set is the “pull down clearance”. This will be where vacuum applied to the choke piston pulls the plate down to after startup. The way the shop manual describes it is very confusing. When you start the car, the choke should be fully closed, and the fast idle speed screw on the highest step of the cam. You should start at around 1500 RPMs...now, you don’t exactly want to put in gear at this speed and take off, so you give the throttle one tap, and the pull-down effect happens opening the choke a crack (approx. 1/8”...this is the drill-bit gauge setting). At this point, the fast idle speed screw should be on the second step marked with the sideways “V” indicator, and your idle speed will drop a step, say to 1,000 RPM. The shop manual makes this confusing, because they mention setting all this up in this position implying that this should be where your choke is set to when cold. That’s not the case, however, it is the position where both of those measurements correspond to each other. The problem is that if you don’t set to the fully closed position, you will never be on the high side of the cam and take full advantage of the fast idle function.