edelbrock carburetor secondarys

Start with the simple stuff and verify that your float levels are correct (per the guides I posted) and your fuel pressure is at 5.5 psi (and does not exceed 6 psi). You may then have to experiment with step-up springs, rods, jets to eliminate the surge in the no-load condition. Maybe the step-up springs in there now are causing it to fluctuate between rich and lean with the vacuum you're drawing at that particular rpm level and no load. Could boomerang back and forth as the rpms rise and fall which in turn affects vacuum levels which in turn affect step-up pistons in the carb. Just a guess.