I am getting a "popping " noise from the carb it sounds like. It happens when the engine is reving down. It almost souds like a bad intake to carb seal (could be) I had the same problem on the last motor I built when I used the same carb. The motor runs perfect, and I get no popping at all when I rev it up, only when the motor returns to idle. If this sounds familiar to you let me know. I think it is probably the carb or the carb gasket, but I thought I should ask first. Thanks

What carb are you using?

I am using a crappy rochester quadra-jet. The carb works, but seems to have a problem opening the secondaries at the right time.

Q-jet secondary opening is easy to adjust, hold the small flat blade screw at the closing link area of the airhorn (top housing), loosen the allen key set screw below and tighten or loosen the flat blade against spring tension to suit your desired opening rate.
If the carb is warped and the secondary plates stick it's time for a rebuild. Check your carb base gasket, if it doesn't match the manifold (heat riser ports etc) it'll suck air.
Nothing wrong with q-jets, many 9 & 10 sec super stockers use them. Great throttle response, cold start, and with some float bowl mods they'll feed 600hp.