I'm busy cutting metal for a bike carb inlet manifold. It would be great if I can keep the tube as short as is practically possible, considering the need for space for welding, etc.

However, is there any sort of minimum length for an inlet tube? Even with a short ali tube on the manifold (~ 3", maybe a little more) there's almost 1" on the rubber coupling tube. In the end there will be around 4" between the hole in the head and the carb itself.

Is this enough?

http://www.jenvey.com/Tech_QA.htm

good page on this