I've ran an edelbrock 650cfm vacuum secondary, Holly 700cfm dbl-pumper, and a holly 600cfm vacuum secondary. These were all purchased new and I never had any problem setting base idle. Of all 3 the Holly 700cfm dbl-pumper out performed the other 2. The 600cfm Holly is a great all around performance carb. no matter what RPM range or load. I am running a 350, edelbrock rpm intake, 1.94/1.60 LT1 bow-tie heads, roller-tipped rocker arms, aluminum push rods, Z-28 valve springs, comp. RV cam, and stock Ram-horn exhaust manifolds.
