I own a 79 z28 and I recently got my carb rebuilt expecting my idle problem to be resolved, but for some reason im still having the same issue.. Whenever i turn on my car, it idles a little high (around 2500 i thnk) and idles down till' 500 and shuts off regardless if its cold or warmed up... Usually i would play with the throttle till it stays on at a steady pace, but as soon as i put it in Driave, it idles low (at and below 500) and shuts off. The only way im able to run it is by immediately tapping on the gas after putting it on drive, but even though it doesnt die while running, it idles low when im at a stop light and usually shuts off unless i place it in Neutral...
I believe the reason why this is occuring is because my spark plug wires are touching the exhaust manifolds, which shocks the hell outta me. I know it couldn't be my carb now, because since the rebuild (yesterday) i noticed a great increase in power and response time, but unfortunately not in fuel efficiency because i have to idle it high..

 

If the plug wires are arching, change them and route them properly.

 

First get the plug wires off the manifolds.
But your problem sounds like you need a carb throttle adjustment.
2500 rpm on a cold engine is from your fast idle cam setting (right side of carb), and it's a tad too high.
As the engine warms up, the choke butterfly opens and the fast idle drops off the linkage cam for it to run on the curb idle setting. And that setting is set too low. Most curb idle screws are at the front drivers side of the carb.
Also check to make sure the choke butterfly is closed (or mostly) with a cold engine, and fully open with a hot engine.
What type of carb do you have anyhoo?

 

I changed the spark plug wires and it didn't change a thing... i believe my carb is a rochester quadra jet 750 cfm. Ill try the fast idle screw, but do you think it could mainly just be from my timing?? I think the day before the problem occurred, my friend changed my timing from 12 to 8. He said he changed it because the sticker says that it should be on 8.. But do the original settings apply for the stock 79 z28 350 apply to my brand new 350 engine?

 

The timing isn't going to make your idle jump up and down like that. I'm still puttin my money (what "change" is left) on a choke/fast idle adjustment. The timing you have it set at is a starting point. Optimum is the most advance you can get before the engine "pings". If it was running good at 12 with no marbles, then put it back there and tell your friend to keep his paws off it!
This should help with the carb adjustment: http://www.hemmings.com/mus/stories/...feature21.html

 

But what about it dying on me wen i put it in either drive or reverse?? I just nw looked at it and at park, the idle ia almost steadily on 1000.. Plus my idle screw is screwed in almost all the way, and im wasting too much gas.. And if i unscrew it any further it might die on me

 

Have you adjusted the two idle mixture screws (front base of carb)? You need either a tuning tach, vacuum gauge, or a real good ear to do it.
Is the choke opening all the way?

 

Yes and yes

 

i had a similar problem with my 78 RS, same carb, i had the wire on the manifold as well, but after that i found out that the choke wasnt opening fully or closing, after i got a new choke and played with it to find a good spot, then i tweeked the idler screw as mentioned above, and my timing was a little off to, im not good at the specific tweeks, but i played around until the car ran properly, also my vacuume tubes were 31 yrs old and rotting through, try that

 

Lol, an old muscle car enthusiast stopped by and helped me out.. Turns out its the gasket thats in between the intake manifolds and carb.. Turns out It wasnt replaced.. So for the mean time, we used carb cleaner, sprayed it, and adjusted the idle and mixture screws. All the symptoms are gon and it runs great, but im guessing now, since my idle is very high, its causing the car to overheat.. Does that sound right to you guys???