03-12-15, 08:56 AM
Just to add to that. The gauge is only measuring the vacuum that's in the intake manifold. Which simplifying it a bit is only effected by two main things the compression of the cylinder (which in your case you can rule out as a problem because you know it was fine before you did the carb swap) and how open or closed the butterfly valve is. The vacuum in that intake manifold can't be directly effected by adjusting idle mixture screws or the internal settings of the carbs BUT and it's a big but how each cylinder is running compared to the other cylinder and so how much vacuum that cylinder is creating compared to the other cylinders is most definitely effected by the mixture settings and all the internals of the carb in the idle circuit so it could be something in the idle circuit of that carb that's causing that cylinder to run differently to the others but I'd still be leaning towards the butterfly valve being out compared to the others. As I said though I'm just thinking out loud I'm not a mechanic so take all the advice with a pinch of salt and a waft of bullshite :lol