I have a 383 Stroker with a large cam and the idle most of the time stays at 1500, turning the carb idle screw does nothing. Someone told me it is because the cam is so large and vacum causes that or something along those lines and cant be lowered due to the size of the cam. It causes the engine to diesel at times wen turned off which is bad.

Most V8s with large cams have a nice low choppy idle, why is mine so high? The timing is fine.

Any help or suggestions are highly appreciated!

I don't know who you been getting your information from but you need to change sources. The reason an engine idles so rough with a big cam is that the carb gets a poor vacuum signal from the engine so the air/ fuel ratio is really inconsistant.
Now for your problem, there is only one reason for the engine to idle that high and that is that the engine is getting enough air in to run that fast. what you have to determine is from where-----is there something other than the idle screw holding the throttle open---like the A/C fast idle solenoid or more likely the fast idle cam part of the choke being sticky or an open vacuum line..........................Dan

Also check your secondary throttle plates, I have two carbs on mine and one was not closing causing the same problem TOO much air.

Sure sounds like a vacumn leak. How do you drive the Elky with that high a curb idle?