Edelbrock 600cfm carb idle will not stay steady

[HeavyHauler]

I have a edelbrock 600cfm carb on a stock 350 chevy except for the usual edelbrock intake manifold. The idle goes up and down and will not stay steady. Also if I shut the engine off and try to restart it then it is very difficult to get started again...I try pumping the gas peddle once or twice but it will not start .....but if I prime the carb by putting gas into the carb from a container it will fire right up but when I get it started the idle will not stay steady. I wanted to be able to drive the truck around while I rebuild the original big block 396 for the truck.

This is a old carb that was on the truck when I purchased it from the last owner that I am just trying to troubleshoot what is wrong with it. Could it possibly be the timing chain and not the carburetor at all?