Porting & Polishing

Some info from SA

Basic cylinder head porting will improve the performance of any production cylinder head by removing flaws that come through mass production. Basic porting does not attempt to correct any design or engineering deficiencies. Once your porting project turns to that, you're beyond the scope of basic porting techniques.

The area of the valve guide that protrudes into the intake or exhaust port is always a place where sharp edges and restriction to flow are found. A basic porting project seeks to smooth those sharp edges.

A more significant point of restriction is where the intake or exhaust port floor curves down to meet the valve seat. Called the "short side radius," it is also a place where sharp edges and roughness pose a threat to flow. In this cutaway of a production cylinder head, the short side radius has not one but two very sharp edges.

With this cutaway, we polished the whole port to better illustrate the rough-to-touch finish.
Note the smoothed valve guides and short side radius.

With this cutaway, we polished the whole port to better illustrate the rough-to-touch finish.
Note the smoothed valve guides and short side radius.