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Re: Porting the head--any ideas? (archive)
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Posted by Kirk McGraw on February 04, 2002 at 22:54:03:

In Reply to: Porting the head--any ideas? posted by James on February 03, 2002 at 22:41:45:

Eliminating the "shoulder" at the port will help airflow. As a general rule, the inexperienced head grinder should confine themselves to smoothing transitions between the port and valve pocket as well as the port and head. Any obvious imperfections are fair game, but avoid changing the shape as you can easily hurt airflow.

A rough surface helps liquid fuel evaporate, which is important for a V-8 with a common wet plenum, but not on an engine with fuel injection in each runner.

A rough surface can promote a turbulent boundary layer, which helps the air "turn the corner" into the valve pocket. Golf balls are dimpled for this reason, and some tuners (Metric Mechanic I think) use this tactic to improve airflow and increase turbulence in the combustion chamber. Sound fluid dynamics.

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