Holley Street Avenger 570 Idling Problems

- Its true that excess fuel pressure can overpower the float valves. the engine will idle for several minutes on the fuel thats in the bowls. If you have an electric pump you can shut it off and see if the idle speed and vacuum come up and if the pump is mechanical you could clamp the rubber line. I clamp the inlet side.
-Have you set your accelerator pump?
-It may just be a leaky powervalve
-I think that cam should be pulling a bit more idle vacuum, at your initial timing.Probably close to 2 more inches.Depends on things like; the cam centerline, and,what idle speed youre targeting.I suggest at least 700rpm target.
- You could crank in some more initial timing.If the engine responds well, dont forget to limit the other end.I kinda think that cam should not need the secondaries cracked, and that may also contribute to the hesitation. Myself, I would try hard to not use that.How far out are the mixture screws?
-With a stable float level, correctly lashed valves,and a properly working power valve,I would be working with; idle speed,idle mix, and initial timing.But before that I would make real sure that there is not a vacuum leak, that the vacuum advance unit is correctly hooked up and not engaging too soon, and that the valves are correctly lashed.Are you running a PCV system? The mains shouldnt be flowing/dribbling at idle.Its also possible to plug the power valve and go for a spin.Mine starts flowing when vacuum falls to about 10 inchs
-If you absolutely cant get it, I would suggest to do a quick check on the position of the split overlap.It should fall within a few degrees of TDC.If it doesnt I would check the cam install.But these are last resort go-tos, since your vacuum is reasonable.
OK, so, good luck.