Thanks for your replies and useful suggestions. The truck had had some major engine mods when I got it such as stage 4 heads so it's quite sporty for 2 and a quarter tons. I think its original carb was kept and a second added, but I suspect the idea of just putting on a duplicate might be behind the over-carburation, but there's nothing to say the bodies aren't warped or some other damage. The 216's or Carters might be the answer, but that's an expensive option if it doesn't work. Maybe if I try blanking one off and seeing what difference it makes it might give me some idea of what's wrong. At least it runs okay, but the fuel cost is too high. I'll try some experiments and get back to you.
