Jim I appreciate your response. This is the kind of information I'm looking for. So their is some good reasons for free port if it's used in the rite combination of things? I see it a lot in my area but it's usually only about .030. This saw however is huge. And the part that puzzles me is that it actually runs hard. Has a home made pop up in it too. Every port has been molested in one way or another.
Free porting 0.030" isn't going to effect much and it's usually as a necessary evil to get the exhaust duration in check on later Stihl models. Still free porting the exhaust is less than ideal, it causes a lot of problems with lower RPM power and throttle response. As RPM's increase the time it's open decreases and its effects decrease.
Jim can get all the kicks he wants out of what he thinks is a "lack of port work knowledge" but there are many other things I can see in that port that suggest a hack job.
1. Upper right corner appears to have a dip in the curvature, anyone who takes any pride in their work would smooth that out knowing that it is a potential ring snag.
2. Obvious waves in port opening in other places. It's not going to kill the saw but it's obviously an unskilled hand at work.
3. Port entrance is very oval shaped, you want more of a rounded corner box with a slight curvature to the roof to maximize time area and get the same mass flow without sacrificing compression height.