We had a 1403? 500 cfm on my son's 318 with a small cam and 273 Commando intake. It ran good but I found an original 4295s, rebuilt it and it runs much better. If I remember right, your original Carb, 4119s, was in bad shape? Some of the Carter 600 cfm carbs would not open the secondaries on the original manifold... I measured a 4294s and it only has 1 9/16 secondary blades. Did you check to see if your secondaries are opening after you installed it? Also the secondary air valve is heavy on the Edelbrock compared to stock Commando.
