Cylinder head porting is the process of increasing the size and smoothing out the rough edges of cylinder head intake and exhaust ports to increase airflow. Improved airflow results in better combustion, which in turn, leads to increased horsepower, torque, and overall engine performance.

IMO choke on an inlet port is not separation, consider a straight short 4V with effectively no short turn. it can simply be too fast (too small port for the engine size and rpm) even though it may be quite a bit less than Mach 1 and be not separating from the turn.

Cylinder Head Porting - Head Porting Basics. Get more power out of your cylinder heads by following five easy rules

However, because there are cylinder head guys out there who do such a poor job hand porting, seemingly haven taken lessons from a blind person with a hammer and a chisel, they help perpetuate the myth that CNC porting is more accurate or “better”.