Using the Port Tuning Nomogram:

Use this chart by drawing a line connecting the box volume and the desired port frequency, 
and extending it through the third vertical column, labled Lv/Sv. From the third vertical 
column, draw a horizontal line across the page. The curved lines that your horizontal line 
intersects indicate the diameter of ports that can be used (in inches and centimeters) along 
them. (Areas are given at the margin for use with rectangular ports.) To get the port length, 
draw a vertical line from the place ytour horizontal line intersects the curved line for the 
diameter, to the bottom of the chart where the length is shown. Add 10% to the port length 
the chart gives. Boxes alaways act smaller than their measured volume would inidcate.   
