SBC Timing Problem

[street3285]

I just finished putting a 383 into my 84 Chevy truck.

At idle, if I rev it, it will stop running, unless I let of the gas quickly. I have to really ease into the throttle to get it to rev up from idle in neutral.

When driving, if giving it gas quickly, it will hesitate and pop through the carb. It has a big hesitation off idle when getting on the throttle, and pops and snaps.
It doesn't have a smooth throttle. I think it is advances way too much, too early.

What can I check? The carb was just built specifically for this engine, so another reason I am thinking it is timing related.

- Travis