McLean, D., Bremfoerder, F., and Hamelink, J., "Development of Headland Ring and Piston for a Four-Stroke Direct Injection Diesel Engine," SAE Technical Paper 860164, 1986, doi:10.4271/860164.
Headland ring pistons and rings were developed for a tractor engine that resulted in significant improvements in horsepower, fuel economy, and reduced smoke over a conventional cutback headland piston while retaining the low bore wear, and bore polishing, and low oil consumption advantages of a cutback headland piston. The ring cross section is L-shaped and the ring has near-zero tension when installed in the bore. Cylinder gas pressure is utilized to create the sealing forces on the bore and ring bottom side. The top of the ring is very near the top of the piston. The performance benefits of this design over a cutback head land piston occurs because of better air utilization and lower average top ring friction. Ring sticking problems are alleviated by the 10° semi-keystone radial tail section. Piston durability problems occurring when the conventional piston was redesigned for the headland ring were resolved.