Open / closed port- Fix my ignorance!

[Great Smokies]

I know a good amount about saw mechanics, but I'm in the dark on the whole open/closed port thing. Would someone educate me please?

 

[pops21]

First off I have to give credit to wigglesworth for these pictures. They are NOT mine but came from a thread that he posted them on. Here is the link to that thread. http://www.arboristsite.com/chainsaw/163039-4.htm


Open port vs closed port has to do with the transfer port that feeds the mixture from the bottom end to the top of the piston to go bang on the compression stroke. This picture says it all. Do you see the difference?
View attachment 311179


Here is the piston difference. The one that has the "windows" is the one that is for the closed port saw. The windows allows the fuel to flow into the transfers. The piston that does not have any windows is the open port saw. The port is blocked off and tunneled by the piston and nothing more.
View attachment 311181

 

[pops21]

Once again in no way am I trying to "steal" this picture either. In both of these posts that I have made I encourage you to click on the links. It will give you a even better idea of the difference between closed port and open port. This picture was posted by gink595 in a thread that I am linking you to here>http://www.arboristsite.com/chainsaw/160103-5.htm

Here is a better picture of the difference. The closed to the left and open to the right.
View attachment 311186

Also every clamshell saw that I am aware of is also open port. Plus it has been noted for a long time now that closed port saws generally make more power.

 

[Michael Bradshaw]

If memory serves me correctly the 268 makes 4.4 HP, the 268XP makes 4.8 HP. For a person that runs a saw every once in a while, you may never feel the extra power, for the person who run saws every day, you will. I have a Husky 268 from 1995, and the saw is a screamer with good torque and plenty of power on the top end. You really have to work at stopping the chain during a cut. The 268 with a sharp full chisel, full house chain this saw made quick work of Oak, Black Walnut, Ash, Maple and anything else put Infront of it. The saw likes to be in the power band near the top end and given time to work. Sharp chain is key.
I don't know if you got the saw, but I do not think you will be disappointed. If you did get the 268 than you most likely see what I mean. Eighter way I hope it works out for you