This is a little long so hope you bear with me and can help. I have a 85 Camaro with a carbed 350, it is all stock but the headers and carb. and manifold that is a Edelbrock RPM performer with a 1406 carb.The carb has been on for about two years and I did not really like it because as it sat for a week or more it would act like it had no gas in it. After I got it running it would have more power and you could always feel the back two kick in. Because I did not like it I went with a holley 4bbl 600 cfm.
I always started good but did not feel like it had the power the Edelbrock had.
After a bit of driving around it would start acting like it was getting to much gas at low rpm's and would die at stops, if I would try to give it a lot of gas real fast or try to pass someone it would just die too.
It would always take a lot of cranking and time before it would start and run.
After a few times of it stopping at lights I went and put the Edelbrock back on and it is doing the same thing now.
I have a heat spacer under the carb. and on the port side I'm getting about 20 pounds of vacuum at idle.
I have chech for vacuum leaks and can find no leaks.in fact if I take th plug off of the port vacuum it idles better. From the first time I had the carb on and now I have not done anything to the motor or the carb.
What do I do now????

 

First thing I would check id the dist. make sure the advance hasnt frozen up.

 

also if it is truly a 350 you need a 650 cfm or 700 cfm carb for it for your performance. the 600 holleys are right on the ragged edge of too small. I suggest putting the 1406 back on after a good cleanup and proper reasembly.

 

ok I just started the car back up and drove it about 20 feet and I checked the the plugs and they were dry and a white with a little tan in them. I checked the vacuum adv. and it is free and working.

 

How does the car run now? Have you tried it with the vacc adv. unhooked?
You will only get a good plug reading if you put the car under load. Exanple would be take it down the track under full power then shut it off. Stop and pull a plug, that will tell you if the carb is running lean. (underload) Something else to concider is are you running the same tank of gas. It is possible you have some weakgas and it is giving you grief. If you are ID throw in 5 gallons of fresh super unleaded run the car for a bit and see if it helps.