by gofaster » Tue Nov 01, 2005 1:48 pm
CSA is the Cross Sectional Area of the port. Check out the spreadsheet section, I think there is something there. If not, I will look at spreadsheets I have saved.
On the spreadsheet you input your port volume, port length, valve size, etc. to get your port design moving in the right direction; opposed to grinding out lots of metal because you think it looks good.
When you're working with irregular shaped ports (none that I work with are perfectly round, square, or rectangular) something you can do is cast a rubber mold of your port, and carefully cut it in equal slices from different representative sections of the port. Say for example that you want to know the CSA at a point where the port shape is complicated by the valve guide boss, or some other restriction. Carefully slice that section from your port mold, making parallel cuts. you can place it in a cup, and stick it to the bottom, and use a graduated buret to fill the cup to a mark just slightly higher than your slice. note the level in your buret, pull the slice off the bottom of the cup, and refil the cup to the mark. You can note the level of the buret, and knowing the thickness of your slice, you can calculate the average CSA for that part of the port. (All of my burets are in cc's, and the rest of my port measurements are in inches, so I have to convert my volume to cu.in.)
There are some bright people on this forum who can explain things better than I do, but I'll be glad to try to help.
Jim