[A Snake]

Just a thought for you. I haven't tried a Demon myself, but I can tell you this: I had the Carb Shop trick out a 750 Holley double pumper for my 427 side oiler. They got it to flow 910 cfm, did four corner idle got rid of the choke horn and race prepped the floats. Once I figured out how to get the idle set properly, the engine ran beautifully. What I'm saying is this; unless you don't plan to run at more than about 3500RPM that carb of yours, if it really is a 625 is a bunch too small. To get rid of the fat idle, try doing what I did and screw the idle screw closed (with the engine shut off) then in half turn increments, starting with 1/2 turn start the engine and see what it does 1/2 turn at a time. Bip the throttle to clear out excess fuel. If it won't idle at 1/2 turn try a full turn and so on. When you get close, with the engine running, turn the screws both directions to find the cleanest idle. the cam you described didn't tell me enough. Lift and duration are only part of the picture. You need to know what lobe center the cam is ground on. 108 degrees or what? It makes a big difference in how the cam acts. If you have a relatively narrow or short lobe center, the cam will be pretty bumpy sounding and hard to find a reasonable idle speed. Also, as I don't know about Demon carbs, but a lumpy cam will give you fits trying to make it idle. The vacuum signal is too erratic. Most folks do the best they can with the idle mixture screws and finish with the curb idle screw.