A trick I learned from an old auto racer, years ago, was to balance the fuel flow in the manifold by gluing a popsicle stick dam across the bottom of the intake runner on the richest cylinder using metal epoxy. The dam is quite short, about 1/8 inch tall and you can adjust the effect by trimming the height and the length across the floor of the runner. If you get it wrong, you just warm up the manifold with a torch and the epoxy lets go and you can start over. Also, if it fails in operation the injested parts will pass through the cylinder without damage.

 

The bottom of the manifold is always wet with fuel when using a carburator and the dam blocks this 'river' of fuel from reaching the rich cylinder. As long as it is kept short and at the entrance to the runner, its effect on airflow is minimal.

 

I know this sounds ridiculous, but I have tried it a couple of times and found it works quite well.

 

Rob