With hydrallic .560 cam you are most likely in the
transfer slot on the Holley carb. When you turn the screw to lower the idle the fuel you had from the transfer slot goes away. You also probably have limited control of the idle screws.
Try raising the angle of the rear throttle blades first slightly and lowering the front blades to get more idle air flow. evenly open up all 4 idle
mixture screws and see if you casn get the carb rich enough to idle correctly.
remove the carb and look at the position of the blades on all 4 barrels. If more than .040 of the
transfer slot is exposed on the front or rear,
drill .090 holes in the throttle blades and reset
the throttle blades for < .040 transfer slot to be visible.
90% of the time poor idle with a non stock cam is
due to idle blade position being wrong. Tom V.
