The recipe card doesn't know what size pipe is being used. The problem occurs at the connection to the manifold. A bigger pipe has trouble being squished down to fit the manifold. The solution would be to bend the pipe according to the card,then weld on a smaller end to fit the manifold. This would save money later if you go to headers or Landgons or a 292 manifold. Don't know how much extra this would costl, you have to decide if it is worth it. Jay6155
