Thanks for replying.

Is there a need to solder a tube to the vent hole on top of the carb fuel pump so as to reduce the effect of pressure variations in the cowl area as shown here :

http://tech.flygsw.org/walbro_carbvent.htm


I am not sure how exactly this helps (given that the inside of the plane is essentially at the same pressure as the outside of the plane).<br type="_moz" />