jester_s1

Those cowl flaps are a good example of using the shape to create a vacuum too. The openings weren't very big, but the angles were perfect. So they were efficient at pulling air through the cowling.

Leroy Gardner

If your muffler is filling the air outlet something else is happening here. With the back portion of bottom of cowl still on it's creating a high pressure pocket for hot air to stack up around the motor box and prevents cold air (at least a large part of it) from entering the inlet openings, the left side opening does nothing to cool the engine it does cause turbulence in the cowl interfering with air on the other side, it's best to block it off. I don't see the need for a baffle but one under the opening to just ahead of the bottom of cooling fins wouldn't hurt.

Use a tack and adjust the needle to richen the engine until it drops the RPM by 300RPM, high speed air over the venture will lean it out to about the right mixture, not doing so will cause a lean engine to run even leaner and the engine to run hotter adding more heat to get rid of and can cause engine to quit or seize up.