600 edelbrock secondary bog.

The orange spring is what the carb comes with from the factory. With my experience, the orange spring works best. I have run a 600 ede on my 360, and love the carb. I finally settled on the 650 ede.

Having said that, I would take the carb off and blow out all the circuits with compressed air.
Then I would check jets,rods, springs, and put the carb back to box stock if isn't already.
At least you will know exactly what you are working with. Recheck the floats. Put it back on, and try it.
Make sure the choke opens all the way. Make sure you adjust the a/f correctly.

On another note....Whats your timming set at ?