I just got my 355 SBC back together and can't set the idle. The engine has and Edelbrock 2 X 4 RPM Air Gap manifold with 2-500 cfm Thunder Series AVS carb's. It has a Comp 280H grind cam with an MSD 8570 small cap distributor, 6A box and no vacuum advance. It fired right up on first start and still does, but wants to idle at 2000 RPM. If I back the timing off to 0 degrees initial advance it will idle down to 800-900 RPM, but the headers soon begin to glow. If I bump it up to 10 degrees, it runs right up 2000 RPM. There are no vacuum leaks at the carb or on the manifold. The linkage is properly adjusted and there are no kinks in the throttle cable. The idle speed screws are backed out and off of the cams. The idle mixture screws on both carbs are out about 1 turn. It has an electric choke on the primary carb and the butterfly is closed on cold starts. The butterfly on the secondary carb is fixed in the wide open position per Edelbrock's instructions. It appears neither carb has a fast idle cam or means of fast idle adjustment like their Performer carbs. I called Edelbrock tech support from work and all they reccomended was 16 degrees initial advance, but I'm afraid that much advance will have it idling at 3000 RPM.