Interesting "how to" article:
and part 2
Another way of generating combustion chamber swirl are "Somender Singh Grooves". They cost almost nothing and are very simple comparing to the Polyquad method.
They can be implemented any time you take the head off!
US Patent 6237579
ABSTRACT: combustion chamber design layout of grooves or channels or passages formed in the squish band to further enhance turbulence in the charge prior to ignition as compared to existing designs with squish bands or hemispherical layouts in I.C. Engines. These grooves or channels or passages after ignition direct the flame front to cause multi point ignition during the combustion cycle resulting in the following distinct advantages over existing designs in practice. First, quicker and complete clean burn combustion; second, lower operating temperatures due to the higher flame velocities; third, enhanced torque and power through the entire range resulting in better fuel economy with lower Emissions; and fourth, smoother engine operation through the entire range enhancing engine life.
Explanation and theory of the Somender Singh Grooves: http://rexresearch.com/singh/singh.htm#4usp
Also, see test reports proving the theory here: http://www.herningg.com/singh/
The first tests were normal engine running tests. These simulated normal types of engine loading as one would see going down the road, anywhere from in town to high speed on the highway. All engine running parameters, dynamometer loading and tailpipe emissions parameters were collected by the computerized data acquisition system. Exhaust gases readings were obtained by a 5 gas exhaust analyzer. Right click to download.
Running Analysis Report. Report is in PDF format. You will need Adobe Acrobat to open this document.
The second tests were ionization current tests. These tests utilized the method of applying a voltage across the spark plug after the coil spark to induce a minute current during the combustion process. This current could then be used as a combustion signature and give insight into many of the characteristics of the combustion process. This report shows graphically the combustion signatures as a function of crank angle. Right click to download.
Ionization Current Analysis. Report is in PDF format. You will need Adobe Acrobat to open this document.
Notice significant carbon deposits (indication of un-burned fuel) in the cylinder squish areas, last pic.