Originally Posted by
Airacobra
I realize this is an older engine but it's brand new and I want to use it. Does this engine have to have a velocity stack sticking outside the cowling to make it run well?
Wow, up for 2 days and no reply.
No, you will likely get better results without a stack sticking out (providing there is at least 1/2 inch clearance for the carb opening).
Changes in air speed past the stack unshielded can cause poor engine performance. I have a Zenoah 20 that lived in the airstream unprotected and worked great. I also had another 20cc (piston ported) that needed the carb protected from the airstream. go figure. Pressure in the cowl can effect both the venturi and the pressure regulator, go figure.
Bottom line is 80% of the time cowled and enough clearance is best (in my experience).