[bdzee]

Just installed a 570 holley street avenger on my 68 327 engine and I could not get the idle down enough so I had to retard the timing down to 4 degrees to get the idle right. I had it previously set at around 10 to 12. Because of this the car is running a little hot and has a slight stumble when I first accelerate. The throttle plates are not sticking and no matter how far down I push the throttles to close and with the screw all the way out it would not idle down unless I turned the dizzy. Any suggestions?

[DjD]

Pull the carb and check the secondary throttle blades... Back the screw out until it isn't seated, then take out any clearence and tighten it about 1/4 turn.

Before that thought, it just came to me that my Avenger's fast idle was set too high. It adjusts under the choke area. Check the instructions, if I remember they say to turn it the wrong way in them...

[Steptoe]

Pull the carb and check the secondary throttle blades

Yep...
If u get a rivet, hammer the end flat and square off, and put a 90 deg bend in it...as a small screw driver...
u can get at the sec adjustment screw, thats on the opposite side to the trottle, under the bottom edge of the carb....close it up (unscrew) till u get adjustment with the main idle stop screw and mixture screws.
Do not adjust so the sec are fully closed...when its like this the butterflys are hard ahainst the carb bores, this can cause jambing and sticking.