440 six pack high idle

I have also heard of warped bases on these carburetors mainly being caused from over tightening be careful of that. When problems like this arise tendency are to continue to tighten things resist that urge! Chasing a problem like this can lead to someone making more changes that are just things that need to be corrected later. Take your time. As suggested before when outboard carbs are in the closed position and return linkage is connected you should be able to tap the linkage rods with your finger and they should wiggle freely in the hole with no resistance of pushing or pulling