I have a 77 280z with a Holley 390 on an Arizona Z car manifold. I'm chasing down an issue with a stumble during light throttle.
I know very little about carbs, but this is what I see: It appears as though moving the throttle doesn't move the cam/pump arm right away. I've adjusted the pump linkage to .015 at WOT, and moved the orange cam to the #1 position, which should bring the accelerator pump in sooner. I've also went up to a #31 nozzle, which eliminated the full throttle stumble. Floats are set correctly and the car idles at 800 rpm. Idle timing is a few degrees advanced from the factory setting.
I have noticed, however, that when the engine is cold, if I move the throttle lever, it moves the cam/pump arm right away, but it'll click after a certain point, and then goes back to not moving the cam/pump arm right away. Is this something with the choke? I made sure the throttle cable is tight from the pedal.
When I'm driving using light throttle, I have to let the car build up to about 2500rpm, and then I can go heavier on the throttle/punch it and have no issues.
This will all be moot soon as I just picked up an LS, but I'd like to enjoy the car this summer.