I have a miss only at idle in my 69 DZ 302. Been trying to adjust the idle mixture on the carb but get erratic rpm's and vacuum readings each time the miss happens making it impossible to set. Miss usually happens about every 5 seconds and sounds like a pre-ignition ping or knock each time the miss occurs or almost like a plug wire jumping fire but have check with the lights off and can see no arc. Have put in new plugs gapped .035, new points and condenser, dwell set at 30*, new rotor ect. Runs great at higher rpms. Cam is a GM over the counter 3927140 off-road and have set timing at 25* advance. Could not find recommended setting for timing with this cam but moving it advance/retard does not seem to make miss get any better or worse. Any help would be greatly appreciated

have you double checked everything, then checked it again? it sounds kind of like a vacuum leak to me. check all hoses and the carburetor baseplate gasket, as well as make sure the intake is tight. is the power brake booster leaking? you will hear that inside the car if it is.
or, perhaps you have the idle lower than it wants to run?

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1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik