porting one of the chain saw engines could be a challange- The ones I have looked into, did not offer much in the way of flow increases-
One can shift ports up -or with great care and work - down.
This is why I like engines with a lot of built in flow potential.
In all my years (too many) of poking into engines - I see the most performance goes along with the best breathing setups.
If tho - one takes a good breather and stuffs it up with a Pi--poor exhaust setup - then the breathing improvements are a waste of time.
The industrial engines were purpose built and the guys who did them really did one fine job in most cases - They were not high performance engines de tuned for sawing logs.
solid ,durable, reliable. You bet.